First you do 3 to the 2nd power which is 9 then you just add 12+9+50= 71
A isn’t correct because there is 2 O’s on the left side and 3 on the right
B is incorrect because there is an S on the right but not on the left
C is incorrect because there are 2 Ca on the left side and 1 on the right
D is balanced as there are 2Na ok each side, 2Cl on each side,2H, and 1 SO4 on each side
Answer:

Step-by-step explanation:

The length of the rope was
yard
Jeff cut the rope into 3 pieces.
Each piece is a different length measured in eighths of a yard which means that the denominator of each piece should be same which is 8
As each piece is of different length so the numerator of each piece will be different.
But the total of the numerator should be 6
So the numerators will be 1, 2 and 3
Since 1 + 2 + 3 = 6
So length of each piece will be
yard
yard
and
yard