How many times greater is the flux from a star that is 5.0 times greater than our sun?

Check the luminosity formulas, you can find there what you are looking for...
(there is also the relation between Flux and Luminosity)

http://en.wikipedia.org/wiki/Luminosity#Luminosity_formulas

Cheers!

The clue (offered as a 'hint') is the ratio. in a ratio the constant multipliers get cancelled out leaving only the bare variables on both sides of the equation ( = ).
If you are out to calculate the Fluxes ratio, then ?, the Stephen's constant gets cancelled out.
If we denote F as the Flux ratio (w.r.t.) Sun & L as Luminosity ratio, 'size ratio' doesn't have a place to stand in this scheme."5.0 times greater" is an unscientific way of  expressing the terms. Does it mean 5 times in radius (then ratio of R is 5.0) or is it volume (in whch case the Radii ratio would be ?5 = 1.71). It can be
"5.0 times greater" in surface area in which case the Radii ratio woul dbe ?5.
I need this information to use in my formula
L = [RT²]²
in which L is expressed as ratio of quantities which are each expessible as "W/m²" at surface (R from its centre) -- Flux per unit area.
1. If I take '"greater" to mean volume => R = 1.71, that leads to
L = 1.71² = 5²/³ = 2.9240
if for the same temperature.
2. If "greater" means Radius (ratio, then),
L = 5² = 25 (again, same temparature).
3. If it is surface that was meant, as you can see the L is the same at 5.0.