Answer:
(a) 25
(b) (5+4)*2 +6 -2*2 -1
(c) see below
Explanation:
(a) evaluating exponents:
6*7 -9*9 +64
Evaluating products:
42 -81 +64
Evaluating sums:
-39 +64
25
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(b) The last three terms of the expression sum to +1, and it is fairly easy to modify the first two terms to make one term that has a value of 18. Then the expression evaluates as 18+1 = 19.
(5+4)*2 +6 -2*2 -1
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(c) Evaluating parentheses:
= 9*2 +6 -2*2 -1
Evaluating products:
= 18 +6 -4 -1
Evaluating sums (left to right):
= 24 -4 -1
= 20 -1
= 19