The product of a number and -4 is at most 24

In a two-digit number the units' digit is 7 more than the tens' digit. the number with digits reversed is three times as large as the sum of the original number and the two digits. find the number.

Why is x= 4 a solution to the proportion 14/x 56/1 6

Which expression is equivalent to 5a/4 - b/8 ?