book Maths Puzzle Numerical Ability

this one I have tryed to work over and over just cant seem to get it

3 + 2 = 5
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x-1 x+1 x^2-1

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book Other Question

(1) simplify: ( sqrt 7 + sqrt 2) (sqrt 7 - 3 sqrt 2)




(2) simplify: sqrt 72 x^5 y^7
Can you please show me how to solve these problems?

1. x/5=-3/25
2. 7x +6=5x-24
3.-92=5t+8
4. 13-(2y+2)=2(y-2)+5y