Help please
10 points if right

Evaluate the expression for the given value of the variable 7a - 4a for a =8

What is the answer to the question 5x+2x

The bottom of ignacio's desktop is 74.5cm from the floor. ignacio's sits in his adjustable chair, and the tops of his legs are 49.3cm from the floor. each clockwise rotation of the knob on the chair raises ignacio's legs by 4.8cm. write an inequality to determine the number of clockwise rotations, r, ignacio could make with the knob without his legs touching the desk