The total weight is 2 1/2 lbs
Rock A is 1/7 of the total weight....so it is 1/7 of 2 1/2 lbs..." of " means multiply
1/7 * 2 1/2 =
1/7 * 5/2 =
5/14 lbs <==
Step-by-step explanation:
Recall that

Therefore,

so


He bought three $10 shirts and six $7 shirts.
20/3 - Take the 6 2/3, multiply the 6 and the 3 (6 x 3 = 18), then add the 2 (18 + 2 = 20). Put that number over the original 3 and you've got yourself a mixed number.