Which problems result in a positive number?

choose all answers that are correct.

a.
–4.2 – 3.1

b.
3 + (–5.4)

c. 7 1/2- (-3 1/4)

d.
–2 – (–3.6)

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.