A = student selected is an eighth grader B = chosen student takes bus P(A) = probability of selecting eighth grader P(A and B) = probability of selecting eighth grader AND student who takes bus P(A and B) = probability of selecting eighth grader who takes the bus P(B|A) = probability of selecting someone who takes the bus given they are an eighth grader
you want to find the mass of only the grapes, not including the bowl. so in this case, you would subtract the mass of the bowl from the total mass. you do this because you dont need the mass of the bowl. 256g - 121g = 135g :)
