Question

the sum of two numbers is 84 one number is three times the other find the numbers

Answer 1

it is 63 and 21 because 21x3=63

Answer 2

x + y = 84
x = 3y

Plug in 3y for x

(3y) + y = 84
4y = 84
4y/4 = 84/4
y = 21

x = 3y
x = 3(21)
x = 63

x = 63, y = 21

hope this helps