Which equation can be used to determine the reference angle r if 7pi/12?

7pi/12 > pi/2, This means it is in 2nd quadrant.
For angles in 2nd quadrant, subtract from pi to get reference angle.

pi - 7pi/12 = 5pi/12

I'll do the first one for you. it isn't very hard at all.on number one, you have (50 × 3), which equals 150, and (3 × 3), which equals 9. after you establish that, you add 150 and 9 together. so, (150 + 9) equals 159.this means that 53 × 3 = 159.