Math
posted by Mary on .
Jane is x years old today. Her brother Kenny is 4 years older. After seven years their total combined age will be 24 years. Write a linear equation for their total combined age after seven years. Fine James age today.

x and x+4 forever
x + 7 + x+ 4 +7 = 2x + 18 = 24 after seven years
2x = 6
x = 3
x+4 = 7
so James is 3 now 
Now:
Jane  x
Kenny  x+4
after 7 years:
Jane  x+7
Kenny  x+11
at that time:
x+7 + x+11 = 24
2x = 6
x=3
Jane is now 3, (where does James come in ? )
...... If you have to do it using 2 variables ....
jane now  x
Kenny now  y
y  x = 4 (#1)
x+7 + y+7 = 24
x+y = 10 (#2)
add #1 and #2
2y = 14
y = 7
x = 3
Same answer, but the first method looked easier.