Hi, sorry i couldn't understand the format of the question, could you post a picture of the question please?
If an integer is chosen between 1 and 50 inclusive, you have 50 numbers total to deal with, so 50 is in the denominator of our ratio (fraction). All the numbers divisible by 3 in that interval total 16 numbers. So the ratio would be 16/50 for a percentage of 32%
The ratio 4 to 7. would be 12 and 21
Risk - 5 = 16. It is just mathematical language.