Given:

9x - 15y = 21 (1)

3x/2 - 5y/2 = 7/2 (2)

Multiplying both sides of equation (2) with 6 we have

9x - 15y = 21

Or, 9x = 21 - 15y (3)

Substituting equation (3) in equation (1) we have

21 - 15y - 10y = 21

Or, -25y = 21 - 21

Or, -25y = 0

Or, y = 0

Plugging y = 0 in equation (3) we get

9x = 21

Or, x = 7/3

Verifying the answer

Putting x = 7/3 , y = 0 in (1)

9(7/3) - 10(0) = 21

Or, 21= 21

Similarly verified for (2) also

Hence verified.