Seven bags of peanuts and 3 sandwiches cost 22. three bags of peanuts and 1 sandwiche cost 8. the cost of 1 bag of peanuts is. one sandwich cost

Replace the informations you don't know with letters.

x = number of bags
y = number of sandwiches

7x + 3y = 22
3x + y = 8

Then solve the equations.
First, isolate the y in the second one like this :
y = 8 - 3x

then replace the y in the first equation with its worth from the second equation :

7x + 3(8 - 3x) = 22

solve for x, then replace the value in the equations to get the value of y