Each question asks for one conversion, in one direction: 20% as a decimal, 75% as a fraction, 0.4 as a percent. One blank per question, so a student is never filling in a row of three and losing track of which is which.
The fractions are written over 100 - 40% is 40/100 - and are not simplified. That is deliberate: simplifying is a separate skill with its own page, and a student who converts correctly and leaves 40/100 has done exactly what was asked.
Divide by 100, which moves the decimal point two places left. 45% becomes 0.45, and 7% becomes 0.07. Going the other way, multiply by 100.
Because that is a different question. 40% is 40/100, and reducing that to 2/5 is the skill our simplifying fractions worksheets ask for. Testing both at once means marking a correct conversion wrong.
The benchmarks worth knowing by heart: 10, 20, 25, 40, 50, 60, 75, 80 and 90 percent. These are the ones that come up in real arithmetic and the ones whose fraction forms are worth recognising.
Sixth grade, usually the first thing taught in a percent unit because everything after it depends on seeing that the three forms are one number.