< P is a right angle.....a right angle is 90 degrees.
< P and < Q form a linear pair....a linear pair, when added, = 180 degrees
so if < P is 90.....and when added to < Q = 180...
90 + Q = 180
Q = 180 - 90
Q = 90 <== so < Q is also a right angle...measures 90 degrees
2.
you had nothing for 1. and I am not sure what you mean by 4.
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To a decimal you can round it down to .5 but if its a fraction no.