Since the triangle is equilateral, QR = RS = QS.
a. MS = (1/2)74
MS = 37
b. Half of the equilateral triangle makes a right triangle. Use Pythagorean Theorem to find QM.
a^2 + b^2 = c^2
37^2 + b^2 = 74^2
1369 + b^2 = 5476
subtract 1369 from both sides
b^2 = 4107
take the square root if both sides
b = 64.1
QM = 64.1