With this quadratic formula problem

We know that

the area of the photo is ------> 4*2-----> 8 in²

the area of entire ad is 8*2-----------> 16 in²
and
the area of entire ad is--------> (4+x)*(2+x)-------> 8+4x+2x+x²
x²+6x+8=16------> x²+6x-8=0

using a graph tool------------> to resolve the second order equation
see the attached figure

the solution is 
x=1.12 in

the answer is
x=1.12 in

You can find the area of a rectangle by multiplying the length and height. so multiply 1/2*7/4(which is the simpler version of 1 3/4) and you get 7/8 as your answer.