Question 174711
let x = the measure of each  of the 3 equal sides and x+8 be the measure of the 4th side of the quad
:
x+x+x+(x+8)=28
:
4x=20
:
{{{highlight(x=5.0)}}}cm

3 equal sides measure {{{highlight(5.0)}}} cm each
4th side is {{{x+8=5+8=highlight(13.0)}}} cm