Help with number 4 I'm stuck on this algebra test with my kid and neither of us understand it

Answer:
a) x = 4
b) x = 8
c) y = -7
d) y = -10
Step-by-step explanation:
Solve by substitution on all
a)
3x + 2y = -5
3x +2 * -17/2 = -5
3x - 17 = -5
3x = -5+17
3x = 12
x = 12/3
x = 4