Question

How do you do this problem?

Answer 1

by substitution is how to solve

2x-3y=21
y=3-x

2x-3(3-x)=21 
2x-9+3x=21
5x=30
x= 6

now substitute our x value into y=3-x
so we get 

y=3-6 = -3

so x=6 and y=-3  hope this helps!!!!! Thank you!

Answer 2

by the use of substitution:for x,

2x-3y=21 ;

will equal 2x-3 (3-x)=21

2x-9+3x=21

5x=30

x=6.

for y:

since y equals 3-x;

y=3-6=-3