I have had a few of these questions (both volume and surface area) and not comfortable with changing the formula over. Any help is appreciated to logical steps for this and other such problems

Question1

A cone has radiusr and slant height l.

A cylinder has radiusr and height r.

Thetotalsurface area of the cone is equal to thetotalsurface area of the cylinder.

Find an expression forl in terms of r.