book Maths Puzzle Numerical Ability

I have a problem with applying the order of operations here are some problems that i have tried: 4^3-5(7-[1])
7(3-9)+12/(-4)

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book Other Question

how do u turn a decimal into a percentage? a two digit number is 6 times its units digit. the sum of its digits is 3. Find the number.
thanks for the help!