Ok, the expression represents the total amount paid because the 4 is the total tax being ADDED to the rest of the expression is 3(26-7). We need to distribute the parentheses by doing: 3*26-3*7. The 3*26 is the three soccer balls multiplied the cost of each ball without the balls being on sale, which is the $26. This brings you to $78. However we then need to do the 3*7, which is the three soccer balls being multiplied by the amount of money you save on each ball being purchased since they're on sale. So that would be $21. Then, $78-$21=$57. $57 is the cost of the three soccer balls without the tax, so we then plug 57 back into the original equation and add 4 to it, since the $4 is the tax. And finally, $57+$4=$61, which is the total amount of money the coach spent on the 3 soccer balls.
For the second part of the equation: Since parentheses comes first in PEMDAS, we need to solve the parentheses first by solving 3(26-7). I've explained how to distribute that in the first explanation above. But basically you just distribute the parentheses using the three, which is 3*26-3*21. You then add four when you finish distributing the equation, since addition comes after parentheses in PEMDAS