Abrand of lightbulb has a power of 8 w and an efficiency of 11.1%. how much power is wasted as heat by this lightbulb?

The sum of all percentages is always 100 %

%converted into light + % converted into heat = 100 %

11.1% + % converted into heat = 100%

% converted into heat = 100% - 11.1% = 88.9%

So, if efficiency is 11.1%, then 88.9% of the power supplied is wasted and converts into heat.

100%8W

88.9%x = 88.9*8W/100= 7.112 W

So, if the supplied power is 8 W, and 88.9% of the power converts into heat, then 7.112 W are converted into heat.