book Maths Puzzle Numerical Ability

would you pleas walk me threw this problem 3(1+4n)- 2(5n-3)=25

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book Other Question

-9x+15=-22-4(x+12)
-9x+15=-22-4x+48
-9x+15=4x+26
15=5x+26
-11=5x
-2.2=x
Please solve:

x^4 - 4x^3 + 3x / x^2 -1

I get x^2 - 4x + 1 - x + 2/x^2 - 1