Question

THREE TIMES ONE NUMBER IS EQUAL TO FIVE TIMES THE OTHER.IF THE SUM OF TWO NUMBERS IS 80,FIND THE NUMBERS.
A SUM FROM SIMULTANEOUS EQUATION

Answer 1

Let the numbers be 'x and y'.
3x=5y
3x-5y=0   ------ equation (1)
x+y=80 --------  equation (2)
Subtract both equation 
(1) ---      3x-5y=O
(2) *5      5x+5y=400   (multiply equation 2 by 5)
              8x=400
x=400/8
x=50
Substitute x=50 in equation (2)
x+y=80
50+y=80
y=80-50
y=30

Checking:
3x=5y
3(50)=5(30)
150=150