math questions for algebra

Question

The sum of one number and a second number is 30. The difference of 3 time on number and twice the second number is 12. Write two equations to represent this system using x for one number and y for a second number 

Answer 1

X+Y = 30

3x - 2y = 12

3x - 2(30-x) = 12

3x - 60 + 2x = 12

5x - 60 = 12

5x = 72

x = 72/5 = 14.4

y = 30 - 14.4 = 15.6

yes it checks 3(14.4) - 2(15.6) = 43.2 - 31.2 = 12