TUV and MNO are supplementary. m TUV=75 and m MNO = (5x).

Supplementary means that the two angles add up to 180 degrees.

If mTUV = 75, and mMNO = (5x)

we can make an equation with them

75 + (5x) = 180

subtract 75 from both sides

(5x) = 105

now divide both sides by 5 to isolate the x

x = 21

now plug the value for x, 21, back into the original

This means that m MNO = 5 (21)

do the multiplication

That equals 105 degrees.

Just to check plug it into the supplementary angle equation

180? 105 + 75

180 = 180

SO, mMNO equals 105 degrees.