The cost in dollars, for school groups to go to a museum can be calculated by
using the expression

$10t+5s$

where $t$ is the number of teachers and $s$ is the number of students.

a) Jamestown school has a group of 3 teachers and 40 students going to the museum.
The cost in dollars, for the group from Jamestown School to go to the museum is $

b) The total cost for a group from Martinsburg School to go to the museum is $290.
If there are 50 students in this group, then there are teachers.