Math help please im having such a hard time..thank you.?

Question

1. x - 15 = 11, x =

2. x/7 = 18, x =

3. 3x + 5 = 41, x =

4. x/12 = 5/36, x =

5. 7/15 = x/9, x =

6. 2.5/x = 12.5/40, x =

7. Is the volume of a pyramid found by using th
the equation V = 1/4*B*h, where B is the
area of the pyramids base?

8. If x = 8, 5x + 15 =

9. If x = 6, 82 - 3x =

10. If x = 10, 3x/5

Answer 1

1. Adding the same value to both sides still maintains the equality. For example, if I say 2+2=4, then we can say
2+2+15=4+15 (19=19 is still true).
So, add 15 to both sides:

x-15 = 11
x - 15 + 15 = 11 + 15
x = 26

2. Multiplying both sides by the same number still maintains the equality. Multiply both sides by 7.

3. 2 steps: subtract 5 from both sides; then divide both sides by 3 (dividing both sides by the same number maintains the equality EXCEPT if you divide by zero, which is not defined -- never divide by zero)

4. Multiply both sides by 12
5. Multiply both sides by 9
(by now, you see that the trick is to get rid of all the things on the same side as x in the equation).

6. Multiply both sides by x (yes, it will work, on the left you will have (2.5*x/x), remember that x/x = 1 (except when x=0) and 1 times anything leaves the anything, in this case 2.5.
The x will now be on the right-hand side.
You will have 2.5 = 12.5*x/40
Multiply both sides by 40;
divide both sides by 12.5

8, 9, 10: simply use the given value in the place of x.

If x = 8, then 5x + 15 = 5*8 + 15 = 40 + 15 = 55

Answer 2

#1-- x-15=11,x=?...find answer by doing the reverse operation
(when subtracting,add and when adding,subtract)so add to solve example_x-30=20, x=50-- 30+20=50
15+11=26 x=26
#2--s/7=18,s=?....do the inverse operation
(when multiplying divide and when dividing multiply)so multiply to solve example_s/9=9 9x9=81,s=81
7x18=126,s=126
#3--3x+5=41,x= inverse operation
first subtract the number without the variable(5) then divide the three with the subtracted answer.
3x+5=41---41-5=36---3/36=12,x=12
#4--s/12=5/36,s=? i totally forgot how to do this one. my teachers would kill me if they found out.
#5--7/15=x/9 same thing for this one
#6--2.5/x=12.5/40,x=? sorry i forgot how to do this stuff.
i guess its summertime. i can't believe i forgot this stuff. never learned the other stuff.

Answer 3

All you have to do is find the value for x. You can do this by doing any operation you like - for example, adding 15, or subtracting 2, or multiplying by 3, etc - so long as you do it to *both* sides of the equation.

So for example with #3,
3x+5 = 41,
so 3x +5 -5 = 41 -5
so 3x = 36
so 3x/3 = 36/3
so x = 12

Hope this helps.

Answer 4

4. x/12 = 5/36, x =
36x=60
x=60/36=20/12=10/6=5/3

5. 7/15 = x/9, x =
15x=9*7
x=63/15

6. 2.5/x = 12.5/40, x =
12.5x=100
x=100/12.5

Hope this helps.

http://sparknotes.com

Answer 5

1. x=26
2. x=126
3. x=12
4. x=5/3
5. x=21/5
6. x=8
7. not enough time to think about
8. 55
9. 64
10. 6

Answer 6

answer to #10

x=10...just substitute in the expression (dah!)

3(10)/5 = 30/5 = 6

The rest is left to the student.