Question 293261
(4+x)(7+x)=4*7+26
28+11x+x^2=28+26
x^2+11x+28-28-26=0
x^2+11x-26=0
(x+13)(x-2)=0
x-2=0
x=2 ans. for the increase.
Proof:
(4+2)(7+2)=4*7+26
6*9=54
54=54