→12-3×(12+1)×2
=12-3×(13)×2----Adding number under the smaller bracket
=12-39×2--Multiplying first two numbers , as Rational numbers satisfy associative property with respect to multiplication.→a×(b×c)=(a×b)×c=(a×c)×b
=12-78
One rational number is positive and other larger rational number is negative, so sign behind result will be that of larger rational number.
= -66
