Total Cost = $26*1 +$0.12*160

I will perform the multiplications first, of course.

It's not shown how you did the two problems. The answers are shown, though.

Well, the answer, -4, for the first problem is correct.

In the second problem, the answer, 4, is correct if the radical sqrt(3*7 -5) is dividing the negative 4.

As it is shown, where there is no slash or division sign between the negative 4 and the radical, thereby saying the negative 4 and the radical are being multiplied, your answer, 4, is wrong.