`a) 5(x-3)(x-7)-(5x+1)(x-2)=25`
`5(x^2 -3x-7x+21)-(5x^2 +x-10x-2)=25`
`5x^2 -15x-35x+105-5x^2 -x+10x+2=25`
`-41x+107=25`
`-41x=-82`
`x=2`
`b) 3(x-7)(x-5)-(x-1)(3x+2)=-13`
`3(x^2 -7x-5x+35)-(3x^2 -3x+2x-2)=-13`
`3x^2 -21x-15x +105-3x^2 +3x-2x+2=-13`
`-35x+107=-13`
`-35x=-120`
`x=24/7`
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