Converting between fractions, decimals and percents, and adding, subtracting and multiplying fractions - all of it without a calculator.
There is no calculator, so the method taught at school is the wrong tool: long division is correct and too slow for an item worth about eleven seconds. What separates people here is a short list of equivalences known by sight - the halves, thirds, quarters, fifths, eighths and tenths - because those are the fractions that produce clean decimals, which is exactly why an item writer reaches for them.
For anything not on that list, go through a power of ten rather than dividing. If the denominator divides into 10, 100 or 1000, multiply top and bottom to get there and read the decimal off: 7/20 becomes 35/100 becomes 0.35, in one step. Going the other way, say the decimal aloud - `thirty-five hundredths` is where the denominator comes from.
Two rules decide most of the marks. Reduce before you look at the options, because an answer that is arithmetically right and not in lowest terms is marked wrong and the unreduced version is usually on offer. And cancel before multiplying rather than after, which keeps the numbers small enough to do in your head.