book Maths Puzzle Numerical Ability

how do i work out this equation?
60=[400/(1+r)^3]

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book Other Question

factor the following:

4x2 - 39x + 27

the 4x is squared

I am not sure if this is factorable or not
how do you work this problem?

solve the matrix equation for x and y.

[1 14] [y-9 14]
[-5x 10]= [5 10]