Alaterala= Pbazei x h prismei
Atotala = Abazei+Alaterala
42 =Abazei +24
Abazei=42-24=18 cm²
baza este triunghi echilateral
A triunghiului lateral=L²√3/4
L²√3/4=18
L²=18*4/√3=72/√3=72√3/3=24√3
L=√(24√3)
P=3*√(24√3)
hprisma=Al/P=24/3*√(24√3)=8/(24√3)=8(24√3)/24√3=(24√3)/3√3=
=(24√3)*√3/9=24*3/9=8 cm