1. Let the fractions be x and y.

x + y = z .......................(1)

x - y = z - 3/4 ................(2)

=> 2y = 3/4

=> y = 3/8

so x + 3/8 = z .........................(3)

and -x + 3/8 = z - 3/4 ..............(4)

=> 2x = 3/4

=> x = 3/8

so the fractions are x = y = 3/8

2. To calculate 7 1/8 - 2 2/3, Lee added 1/3 to 4 1/8. Why do you think that Lee did this?

2 2/3 is almost 3. so what Lee did was to subtract 3 from 7 1/8 to get 4 1/8. But now, since 2 2/3 is actually not 3, he had to make up for subtracting a greater number by adding the difference. (the difference between 2 2/3 and 3 is 1/3).