Complimentary angles always add up to 90, they are right angles. As I explained earlier Supplementary angles were half of a full circle which is equal to 360°, this time we are talking about complimentary angles which are 1/4 of 360.
Any picture? Example: if the number is 36 you would round to 40 and if the number was 34 you would round to 30 if it is 35 you choose what to round to. It depends on the last digit.
