Photo math is a good way to do it it works it out and all I use it and it helps me understand
Answer:
C. 6 cm
Step-by-step explanation:
A P E X
Your answer is the third option.
we have

Using a graph tool------> to resolve the second order equation
the solution is

so

therefore
the answer is the option
length = (x + 18) inches and width = (x + 9) inches