4^2 – (2 + 3) x 3 = 1

17 – 25 – (1 + 3) x 5 = 12

So in the first problem, the ordinary way of solving the problem would be to multiply 3 and 2 first. So the problem becomes 5 + 6 – 4 + 1, or 8.

Parentheses change the order of calculations — you do whatever is inside the parentheses first, using the same rules for what’s inside them. They want you to find some sets of parentheses or brackets — you can nest parentheses inside brackets, as in [2x(3+5)-4].

The second problem, solved without any parentheses, gives you an answer of 25. To get it to equal 1, you have to find someplace to put parentheses to make the answer a lot smaller than that. Hmmm… well, if you subtracted everything after the minus sign, that would make the answer smaller. So if you write the question as 4^2 – (2+3×3), the problem becomes 16 – 11. We’re making progress, but not there yet.

How about 4^2 – (2+3)x3? That’s 16 minus 5 times 3, or 15. Bingo. The parentheses tell you to do the addition inside first.

In the last one, you can get the answer if you can find a way to subtract 5 from 17. OK…if you add the 1 and 3 together first and multiply it by 5, that’s 20. -25+20 is -5, just what you want. So write it as 17 – [25 – (1+3) x 5].

That leaves the first one, and I can’t see an answer. Are you sure you typed it correctly?

PS: (5+3) x 2 – 4 + 1 = 13, not 15.