maths LINEAR INEQUALITIES IN ONE UNKNOWN F.3數2

let the width of the rectangle is x
then the length of the rectangle is x+4
the length of each side of an equilateral triangle is also x+4
the sum of the perimeters of the equilateral triangle and the rectangle
=3(x+4)+2(x+x+4)
=3x+12+4x+8
=7x+20
since
7x+20<=69
x<=7
we conclude that it is impossible that the width of the rectangle is 7.2CM