What's the missing output value ? ?

Aclass consists of 55% boys and 45% girls. it is observed that 25% of the class are boys and scored an a on the test, and 35% of the class are girls and scored an a on the test. if a student is chosen at random and is found to be a girl, the probability that the student scored an ais

You use technology ans find a sum of 6.712e-8. write this sum in standard form

Me because i don't understand how to do it.: )