Pouvez vous maider pour la questuon deux merci

How do you find principle and simple interest

3.4a=57.8 what is the the value of a

Afactory buys 10% of its components from suppliers b and the rest from supplier c. it is known that 6% of the components it buys are faulty. of the components brought from suppliers a,9% are faulty and of the components bought from suppliers b, 3% are faulty. find the percentage of components bought from supplier c that are faulty.