Me out on my last questions for 50

7.at jessica’s school, students can buy scientific calculators for $15.00 each. graphing calculators cost 5 times that amount. if $345.00 worth of calculators were sold and 3 of those were graphing calculators, how many scientific calculators were sold?

8.for a set of three consecutive odd integers, three times the largest integer is 7 less than twice the sum of the other two integers. what is the largest integer in the set?

9.two trains are traveling towards each other at a constant speed.
the trains are currently 714 miles from each other.
the speeds of the trains differ by 8 miles per hour.
the trains will meet in 7 hours.
what is the speed of the faster train?