Pls i help with this circles problem for math. and no links pls?

Jenisey has $24 to spend on seven pencils. after buying them she had $10. how much did each pencil cost.?

The half-life of a certain material is 0.002 second. approximately how much of a 14-gram sample will be left after 0.004 second? a. 12 grams b. 3.5 grams c. 0.06 gram d. 7 grams

What is the measure of ba (the minor arc) in the diagram below?