(3x+1/2)+(7x-41/2)what is the answer

Ricardo ran the 400 meter race 3 times his fastest time was 54.3 seconds his slowest time was 56.1 seconds if his average time was 55.0 seconds what was his time for the third race

Empty box + box + empty box fill in the box is equal to 30 how

Thelime contains the point(-3,0) and parallel x-3y=3( show all work)