Write the sentence as a equation

the product of 248 and a is 391

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Jared had 3/7 of the minutes on a family phone plan remaining for the month. the plan is shared by 2 people. if divided equally what portion of the minutes remaining on the phone plan would be avalible for each person

Mabel paid $2.95 for a granola bar dimes and quarters. she used five few were quarters then dimes. how many dimes and quarters did she use to pay for the granola bar.