Respuesta :
j = # of jars
b = # of buckets
y = total # of rocks
2j + 3b = y (2 rocks per jar, 3 rocks per bucket)
Because Joy has 3 jars you can plug 3 in for "j", and because she has 4 buckets you can plug in 4 for "b"
2(3) + 3(4) = y
6 + 12 = y
18 = y