You can either change 86% to a decimal fraction, multiply the decimal fraction times 150 to determine how many you got right and then subtract that number from 150. Or you could take the decimal representation of 86% and subtract that from 1 to get a decimal representation of the fraction you got wrong and multiply that times 150. Either way, there is one percent to decimal conversion, one multiplication, and one subtraction.
John
My calculator said it, I believe it, that settles it