Question 142029
Two brother, x & y
:
Write an equation for each statement:
;
"The sum of the ages of two brothers is 24 years."
x + y = 24
y = 24 - x; use for substitution
:
"In three years time, the elder brother will be twice as old as younger brother."
(x+3) = 2(y+3)
x + 3 = 2y + 6
x = 2y + 6 - 3 
x = 2y + 3
:
how old are the brothers?
:
Substitute (24-x) for y
x = 2(24-x) + 3
x = 48 - 2x + 3
x + 2x = 51
3x = 51
x = {{{51/3}}}
x = 17 yrs 
then
24 - 17 = 7 yrs is y's age
;
:
Check solution in the statement:
In three years time, the elder brother will be twice as old as younger brother."
20 = 2(10)