Question 849671
let j = Joe's age
let b = brother's age
:
Write an equation for each statement:
"Joe's brother is 6 years older than Joe."
b = j + 6
" Two-thirds of his brother's age is 3 years more than three-fourths of his age."
{{{2/3}}}b = {{{3/4}}}j + 3
Multiply by 12 to get rid of the denominators, then you have:
8b = 9j + 36
Replace b with (j+6) from the 1st statement
8(j+6) = 9j + 36
8j + 48 = 9j + 36
48 - 36 = 9j - 8j
12 = j
 How old is Joe? 12 yrs old
:
:
Check this, we know brother is 18 then
 Two-thirds of his brother's age is 3 years more than three-fourths of his age."
{{{2/3}}}(18) = {{{3/4}}}(12) + 3
12 = 9 + 3; confirms our solution