3x-2=13
Transposing -2 to RHS, we have
Or                              3x=13+2
                                 3x=15
Or                               x=               (Dividing both sides by 3)
Or                               x=5

5x-9=8
Transposing 9 to RHS, we have
                                         5x=8+9=17
 ∴                                           x=                     (Dividing both sides by 5)

x-2=7
Transposing (-2) to RHS, we have
                                     x=7+2
∴                                    x=9

y + 3 = 10
Transposing 3 to RHS, we have
                                       y = 10 - 3
∴                                      y = 7