Assume number =x,
x(2x+5) = 75
=> 2x^2 + 5x -75 = 0
=> 2x^2+ 15x -10x -75 =0
=> x(2x+15)-5(2x+15)=0
=>(x-5)(2x+15)=0
x = 5, or x = -15/2
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