twice one number added to three times another number is 21

Question

find the numbers, if the difference between them is 3

Answer 1

2x + 3y = 21

 

x - y = 3

 

x = 3 + y

 

substitute for x so 2(3+y) + 3y = 21

6 + 2y +3y = 21

 

 

you can calculate y and then from that, x