Let’s represent the length of the rectangle as x and the width as y.
So always try to make a relationship between the unknowns so you don’t have a lot of variables
Now
The length of the triangle could be represented by width+7=length in other words y+7=x
So you could substitute x in the equation of x*y=144
(Y+7)(y)=144
So y^2+7=144
Y=11.7 x=18.7
