Which relationship is always true for the angles x, y, and z of triangle mnp?
x+z=y
y+z=x
x+y+z=180 degrees
x+y+z=90 degrees

The mass of a marine organism, in pounds, p years after it is born is given by the polynomial function r(p) = -4p2 + 300p. find the mass when p = 20 years.