equations in two unknowns , grade 9, question 6

01/03/2017 Grade 9 4,480


1)Solve the system :

\left\{\begin{gathered}x=120-y\hfill\x=3y- 4\hfill\\\end{gathered}\right.

2) Find the dimensions of  a rectangular mat knowing that its perimeter is 240 cm and its length is 4cm less than triple its width.

3) knowing that 30% of the carpet is black and the rest is brown, determine the brown area.