Stefan sells Jin a bicycle for $138 and a helmet for $16. The total cost for Jin is 40% of what Stefan spent originally to buy the bike and helmet. How much did Stefan spend originally?

Stefan originally spent $61.60.

Explanation:
Equation: 40/100=x/154
100 is the whole because it is 40% out of a hundred. 154 is the sum of how much Jin bought the bike and helmet for. You would then be able to simplify 40/100 to 4/10. 154 divided by 10 would be 15.4. You would do the same to the numerator, so multiply 4x15.4. That would give you the 40% of what the bike and helmet were originally bought for.

For the first question the answer is a, for the second c, for the third d, for the 4th b, for the 5th a