in order to find the missing angle of U we need to know the two other angles.
We know that ∠T is 65° and we know that ∠TSF is 105°. Because ∠TSF is an exterior angle, we can subtract 180 to get the interior angle. This would mean that ∠S is 75°.
Using this we can add 65 to 75 then subtract the total from 180 to get ∠U.
