Question 1023729
When you're 3/4 your age, I am 4x yours. When you are my age our total equals 140. 
:
a = your age
b = my age
let d = (b-a) the difference in our ages
:
When you're 3/4 your age, I am 4x yours
 d = 4({{{3/4}}}a) - {{{3/4}}}a
 d = 3({{{3/4}}}a)
 d = {{{9/4}}}a
replace d with (b-a)
b - a = {{{9/4}}}a
multiply by 4
4(b-a) = 9a
4b - 4a = 9a
4b = 9a + 4a
4b = 13a
b = {{{13/4}}}a
b = 3.25a
:
"When you are my age our total equals 140. "
a + d + b + d = 140
replace d with (b-a)
a +(b-a) + b +(b-a) = 140
3b - a = 140
replace b with 3.25a
3(3.25a) - a = 140
9.75a - a = 140
8.75a = 140
a = 140/8.75
a = 16 yrs is your age
Find b
b = 3.25*16
b = 52 yrs is my age
:
:
lets see if that works out
"When you are my age our total equals 140. " 
52 - 16 = 36 yrs, the difference in our ages
When your(a) age  is 52, I(b) will be: 52 + 36 = 88. 88 + 52 = 140