Im having trouble understanding formulas. Can anyone help me with these problems?

Question

y=13+x, for x.

y=5x, for x.

a+bc, for c.

y=x+b, for x.

y=5-x, for x.

By=Ax, for x.

A=at+b, for t.

Answer 1

Note: The variable (that I keep refering to, at least) is the letter that you're solving for if you didn't know that already.
1. If anything is added to the variable, simply subtract it from both sides. It will cancel out the :anything" on one side and subtract "anything" from the other.
y=13+x
-13 -13
y-13=x

2. If the variable is multiplied by something, divide both sides.
y=5x
y/5=(5x)/5
y/5=x

3. I'll assume this one is a=bc, since you can't solve for anything without an equal sign.
Now, you divide both sides by b.
a=bc
a/b=(bc)/b
a/b=c

4. Subtract b from both sides.
y=x+b
y-b=x+b-b
y-b=x

5. When you subtract the variable, you have to SUBTRACT the number in front of it (unless it's negative) and multiply everything by -1. If one of the numbers comes out positive and the other negative (like in -5+3), switch the numbers around (3-5).
y=5-x
-5 -5
y-5= -x
-1(y-5)= -1(-x)
-y+5=x
5-y=x

6. Divide by A.
By=Ax
By/A=(Ax)/A
By/A=x

7. Subtract b first, divide second. Since one "a" is capitalized and the other isn't don't cancel out the "a"s.
A=at+b
A-b=at+b-b
A-b=at
(A-b)/a=(at)/a
(A-b)/a=t

Answer 2

make the term they request for the subject, meaning x = something... or t = something...

y=13+x, for x
Since they wants x, make the equation to be x = something. In this case:
y = 13 + x
Minus 13 on both side of the equations to remove 13.
y - 13 = 13 + x - 13
y - 13 = x
Therefore, x = y -13 (THAT'S IT!)

Ok, another one...
y = 5x, for x
For this eqaution, to remove that irritating 5, divide both sides by 5.
y = 5x
y / 5 = 5x / 5
y/5 = x
So, x = y/5

Next one, a+bc for c.
Suppose a + bc = 0. (You didn't state so i suppose you missed it)
a + bc = 0
since you want c, 'drag' all the terms with c inside to one side.
bc = -a
With the same techniques you leanrt earlier, make c the subject.
So,
bc/b = -a/b
c = -a / b

Try working out the rest with these methods. You'll learn only when you try. =)

Answer 3

You mean "solve y=13+x, for x"? A formula is just an equation set to a single variable, so just use algebra to solve each equation for the given variable. The third one doesn't make sense unless you meant a=bc and not a+bc.

Answer 4

you need to solve for those variables(x)

so for .... the answer would be

y=13+x

1. x=13-y

y=5x
2. x=5/y


3. hmmmm?
wheres the =

4. x=y-b


u can do the rest

Answer 5

these are not formulas i say

these are simple math equations (algerbraic) that looks for the value of a certain variable, where in your examples you mostly look for the value of x

they are easily solvable by simple math rule
for example

y = 5 - x
x = y -5

instead of looking for the value of y, we just re-write the equation to look for the value of x

Answer 6

x=y-13

x=y/5

if you meant a=bc
c=a/b

x=y-b

x=5-y

x=(By)/A

t=(A-b)/a