First we start by finding the two number we are making a ratio 24 ,42 and 18, after we find this we then simplify this like a fraction 24 ,42 and18 have 6 in common so we divide them by 6 (if you're learning raitos I would assume you already know how to simplify fractions), after that you get 4:7:3.
637 is the answer because our value is 980 we all know the unknown value with x for the step above 980 and 100% and 65% is the result in a pair of a simple equations