Yes, we need the sisters age to find it the answer, not trying to be rude we just need the sisters age.
-10/40 = y / -5
cross multiply
(40)(y) = (-5)(-10)
40y = 50
y = 50/40
y = 5/4 <===
Its impossible to draw a trapezoid with just three right angles.
a trapezoid has 4 sides, which means all the angles inside the trapezoid must add up to 360 degrees.
if you have just 3 right angles (90x3), you already use up 270 degrees. Leaving you with just 90 degrees left, which is also a right angle. That means, there has to be four, if you have at least 3.