a) 19.5 - x * 6.3 = 11.625

First, distribute the negative sign:
19.5 - 6.3x = 11.625

Next, subtract 19.5 from both sides:
-6.3x = -7.875

Divide by -6.3 to solve for x:
x = -7.875 / -6.3
x = 1.25

b) 4.75 + x / 9 = 34.266

First, subtract 4.75 from both sides:
x / 9 = 29.516

Next, multiply both sides by 9 to solve for x:
x = 29.516 * 9
x = 265.644