His is just a matter of converting 5% into a decimal =5/100 = .05. Take this value and multiply it by $350,000. The result is the amount of commission that Tamara made (.05)*350,000=$17,500 To make sure that this is correct we know that 10% of 350,000 is $35,000. Half of this value is equal to 5% and that is $17,500.