To solve the first equation:

16 - (9 1/2)y = 3y + 21
16 - 9y - (1/2)y = 3y + 21
16 - 9.5y = 3y + 21
-9.5y - 3y = 21 - 16
-12.5y = 5
y = 5 / -12.5
y = -0.4

To solve the second equation:

(1 1/4)y + 7.5 = 5y
(5/4)y + 7.5 = 5y
(5/4)y - 5y = -7.5
(5 - 20)y = -7.5
-15y = -7.5
y = -7.5 / -15
y = 0.5

Therefore, the solutions to the two equations are y = -0.4 and y = 0.5.