The answer is correct because—and I oop reeeee blah blah reee
First you need to subtract 35 to get one equation =0.
x^2-10x-10=0 then use the quadratic formula (let me know if you need the formula of need to see these steps)
and solve to = approximately 8.87 and 1.12
The answer is x<20. Hope that helps.
I used the completing the square method to get the (x+2)^2. The final line is in standard form.