The sum of two numbers is 73. Find the numbers if one number is 15 less than three times the other.
x + y = 73
(x-15) = 3y ------> x = 3y + 15
Substitute
(3y + 15) + y = 73
Collect like terms
3y + y = 73 -15 ------> 4y = 58
Divide by 4 to isolate y
4y/4 = 58/4 ------------> y = 14.5
Substitute into given equation x + y = 73
x + 14.5 = 73 ---------------> x = 73 - 14.5 -------> x = 58.5
Thus y = 14.5 and x = 58.5