how do i do this -3x-7=18?

Question

i'm trying to do a practice test for extra practice but i don't even understand the practice i'm getting a littel sleepy. so if some one could help me understand some of these one i think i could figer it out for the rest.

1. "solve each equation.then check your solution."

-8(4+9r)=7(-2-11r)


2."solve each proportion."

2/10=1/a

3. y/4=y+5over 8


4."postage"
in 1975, the cost of a frist class stamp was 10senice. in 2001, the cost of a first class stamp became 34senice. what is the percent of increase in price of a stamp?

if any one can help me out with understanding what i'm doing i would be very thankful.

Answer 1

1.-32-72r=-14-77r
5r=18
r=3.6

2.2/10=1/a
2a=10
a=5

3.y/4=(y+5)/8
8y=4y+20
4y=20
y=5

4.%age increase=(34-10)/10*100=240%

Answer 2

How do i do this -3x-7=18?

-3x=-11
x=11/3

i'm trying to do a practice test for extra practice but i don't even understand the practice i'm getting a littel sleepy. so if some one could help me understand some of these one i think i could figer it out for the rest.

1. "solve each equation.then check your solution."

-8(4+9r)=7(-2-11r)
-32-72r=-14-77r
5r=18
r=3.6


2."solve each proportion."

2/10=1/a
1/5=1/a
a=5

3. y/4=y+5over 8
y/4=(y+5)/8
2y=y+5
y=5


4."postage"
in 1975, the cost of a frist class stamp was 10senice. in 2001, the cost of a first class stamp became 34senice. what is the percent of increase in price of a stamp?

34/10=3.4
3.4/1=2.4 or 240% increase

Answer 3

Okay, question 1. First thing you're going to do is multiply everything out to make it easier. That gives you:
-32-72r= -14-77r. You are going to add 14 to each side. This cancels out the -14 on the right side of the equation, and gives you 77r by itself. Now add 72r to each side. Your equation should now look like this:
-18=-5r. Divide both sides by 5 to get r by itself, and you get:
-18/5=r.

Question 2.
Simplify the left side of the equation to get your answer. 2 and 10 are both even. Divide both by 2, giving you 1/5, and a=5.

Question 3.
Multiply both sides by 8 to get rid of your denominators. This gives you (8*y)/4=y+5. The 8/4 can be simplified to 2y. Subtract the y on the right side of the equation from each side, giving you y=5.

Question 4.
All of the background knowledge makes this one seem more complicated than it really is. To find the % increase, all you have to do is divide 34 by 10. This gives you 3.4. Multiply that by 100 to get the percentage, and the cost of a first class stamp increased by 340%.

Hope this helped. Good luck with your homework.

Answer 4

1. distribute on both sides
-8(4+9r)=7(-2 -11r)
which becomes
-32-72r=-14-77r

add 77 on both sides

-32 +5r= -14
add 32 to both sides to balance both sides out

you get: 5r= 18
divide both sides by 5 to get "r"
5r/r= 18/5
r=18/5

2. 2/10=1/a
cross multiply to get 10=2a
divide both sides by 2 to get "a" value: a=5

Answer 5

-3x-7=18 Can be done with the basics of getting 'x' by itself. 1st you add 7 to both sides because you want to get -3x by itself. And now we have -3x=25. Then you divide -3 to both sides, again to get 'x' by itself and you are left with x= -25/3, or x= -8.333. Hope this helps. Good Luck.