The complementary event is that a customer does not enter the store within one minute of closing, and the probability is 75%.
The complement is found by subtracting from 100%; 100-25 = 75%.
I put in a graph and the equation
y<2x-5
y>-3x+1

make denomenators the same
we have
x+4 and 3
times the fraction with x+4 in denomenator with the fraction 3/3
times the fraction with 3 in denomenator with the fraction x+4
we get

since common denoms, can add them to get


that is simplified