Estimate the measure of the angle

Hundred and tens tables to make 430 in five different ways

Consider this expression and the steps to evaluate it. 4^5(−2)^9/4^8(−2)^3 1. apply the quotient of powers:      (−2)^a/4^b 2. evaluate powers:           c/d select the value of each variable. a = _ b = _ c = _ d = _

Why is causation so much more difficult to prove than correlation?