(x+5)^2-x^2= 145

x^2+ 10x+25-x^2= 145

10x+25= 145

10x= 145-25

10x= 120

x= 12

Original area =12×12 =144 square meters.

I hope it helps you. Please adopt it in time if you are satisfied.

Your adoption is the motivation for my answer!