I am not sure which property to use to write this as a single definite integral. I took a shot in the dark and thought about this problem as simply adding the net area under the curve of three different functions but this didn't help much. I guessed at the answer being the sum from -2 to 5 of f(x)dx. Im almost positive this is wrong, a hint may help.
Is it clear that the first two integrals added together would yield the net signed area under the curve from -2 to 5? The third integral is taking away (because of the subtraction) some of this area. What are you left with?