(3/4)*[12*4+(-16)]+(-20)
PEMDAS is order of operations...
Parentheses first, exponents next, multiplication/division, finally addition/subtraction.
So the first thing you need to address is the innermost parentheses
(3/4)[12*4-16]+(-20) now you have multiplication in one set of parentheses
(3/4)[48-16]+(-20) now you still have addition/subtraction in the middle parentheses
(3/4)(32)+(-20) and you have a multiplication in for the last parentheses
(3/4)(32)-20 we have multiplication on left side
96/4-20 now we have division on left
24-20 and finally subtraction
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