What does B equal ?

The angle A is equal to B because they are opposite angles by the vertex.

So...

5x - 15 = 2x + 21

For solve it, we are going to do the same operations in both sides of the equal sign. We need put all the X in a side of the equal sign and all the free numbers in the other side.

5x - 15 = 2x + 21

We are going to add 15

5x - 15 + 15 = 2x + 21 + 15

5x = 2x + 36

We are going to substract 2x

5x - 2x = 2x + 36 - 2x

3x = 36

We are going to divide by 3

3x/3 = 36/3

x = 12

and

b

step-by-step explanation:

step-by-step explanation:

given perimeter: 28cm

length: 9cm

atp,

2(l+w)=p of the reactangle

2(9+x)=28

18+2x=28

2x=28-18

x=10/2

x=5

therefore width is 5 cm