The sum of two numbers is 91. if three times the smaller number is subtracted from the larger number, the result is 7.7. find the two numbers.

if x is the bigger num and y is the smaller

x + y = 91
x - 3y = 7.7

multiply by -1

x+y = 91
-x + 3y = -7.7

add the equations

4y = 91 - 7.7
4y = 83.3
y = 20.825

then x+y = 91 use to find x

x+20.825 = 91
x = 70.175

the two numbers are 70.175 and 20.825