Answer:
C. 17 units
Explanation:
Surface area of rectangular prism is given as:
A = 2lw + 2lh + 2wh
A = 930 square units
l = 12 units
h = 9 units
w = ? (We're to find the width)
Plug in the value into the formula
930 = 2*12*w + 2*12*9 + 2*w*9
930 = 24w + 216 + 18w
Add like terms
930 - 216 = 42w
714 = 42w
Divide both sides by 42
714/42 = 42w/42
17 = w
w = 17 units