15. 
Add "g" on both sides
Multiply 5 on both sides to get x by itself
x = 5(a + g)
x = 5a + 5g
18. a = 3n + 1
Subtract 1 on both sides
a - 1 = 3n
Divide 3 on both sides to get n by itself
= n
21. M = T - R
Add "R" on both sides to get "T" by itself
M + R = T
24. 5p + 9c = p
Subtract "5p" on both sides
9c = p - 5p
9c = -4p
Divide 9 on both sides to get "c" by itself
c = 
or c = 
27. 4y + 3x = 5
Subtract "4y" on both sides
3x = 5 - 4y
Divide 3 on both sides to get "x" by itself
x = 
x = 
The area of a circle is given by
We can solve this equation for r: divide both sides by pi:
Consider the (positive) square root of both sides:
So, in your case, we have
The definition of the interior angles of a triangle states that
interior angles of a triangle add up to 180º.
This means we can find the measure of <CED:
<C
ED + <E
CD + <C
DE = 180º
<C
ED = 180º - <E
CD - <C
DE
<C
ED = 180º - 43º - 35º
<CED = 102º
By the definition of vertical angles states that a pair of vertical angles are congruent.
This means <C
ED = <A
EB
If <C
ED = 102º
Then
<AEB = 102º
By definition of the interior angles of triangles:
<AEB + <EBA + <BAE = 180º
<AEB = 102º
<EBA = 18º
102º + 18º + <BAE(<A) = 180º
<BAE = 180º - 102º - 18º
<BAE = 60º
<BAE is another way to say <A
<span>
m∠A = 60º</span>
