If stock beta is 1.2 the risk free rate is 4 and market rate of return is 14 what is the market risk premium?

I'm going to assume that you mean the risk free rate is 4%, or 0.04, and the market rate of return is 14%, or .14. If that is the case, then we solve:

Market Rate of Return = (Risk Free Rate) + Beta * (Market Risk Premium)

0.14 = 0.04 + 1.2 * MRP

0.1 = 1.2 * MRP

0.1 / 1.2 = MRP

0.08333... = MRP

The Market Risk Premium would be approximately 8.33%

This is an example of the Capital Asset Pricing Model, or CAPM.