Chemistry
posted by Sarah .
In 2.00 min, 28.4 mL of He effused through a small hole. under the same pressure and temperature, 9.69 mL of a mixture CO and CO2 effused trough the hole in the same amount of time using the following mathematical formula relating rate of effusion to molar mass(M), Calculate the average molar mass of the mixture CO and CO2.
Explain it step by step and provide with formula.

There is no explaining. It appears the formula you need is provided. It's a matter of substituting the numbers and solve for the molar mass of the mixture.
(rate1/rate2)= sqrt(M2/M2)