The answer should be 42 times.
Answer: Click on the cell where you want the result of the calculation to appear. Type = (press the equals key to start writing your formula) Click on the first cell to be added (B2 in this example) Type + (that's the plus sign)
Step-by-step explanation:
Angle C and the 112 degree angle are supplementary, so angle C measures 180-112=68 degrees.
This means that by the exterior angle theorem, 
123 divided by 20 which equals 6.15 and then multiply 6.15 by 31 and the answer will be $190.65