Answer:
The dimensions are 4 millimetres by 10 millimetres
Step-by-step explanation:
The area of the first rectangle is 5*8=40 square millimetres. Let's call the width of they yellow rectangle w, and the length l. Now you can set up the following system of equations:
l*w=40
2l+2w=28
Isolate one of the variables to substitute:
l=40/w
2(40/w)+2w=28
80/w+2w=28
Multiply both sides by w:
80+2w^2=28w
Move everything to one side:
2w^2-28w+80=0
Factor the quadratic:
2(w^2-14w+40)=0
2(w-10)(w-4)=0
w=4 or 10
l= 10 or 4
Hope this helps!
