If integral(0 to 2)f(x)dx = 4.35 and integral(2 to 4)f(x)dx = -2.75 and integral(2 to 4)f(x)dx = 3.15 then

what is:
1. integral(2 to 4)(1 - f(x))dx
2. integral(2 to 6)|f(x)|dx
3. F(6) - F(4) where f(x) = F'

You have mis-copied one of your integrals. I think your third one should be integral(2 to 6)
1. =integral(2 to 4) 1dx - integral(2 to 4)f(x)dx=2- -2.75=4.75.
2. = -2.75+3.15=0.4
3.F(4)-F(0)=4,35+-2.75=1.6
F(6)-F(0)=4.35+ -2.75+3.15=4.75 so F(6)-F(4)=4.75 - 1.6=3.15