Which of the following is not a characteristic of primates?
a. binocular vision
b. walking upright
c. flexible shoulders
d. opposable thumbs

Step-by-step explanation:

X = cost of PB  

Y = cost of J

6X + 4Y = 1932  <--- price is in pennies

5X + 3Y = 1567 <--- price in pennies

Dividing everything in the first equation by 2:

3X + 2Y =  966 <--- price is in pennies

5X + 3Y = 1567 <--- price in pennies

Elimination method... let's multiply the first equation by 3 and the second equation by -2.

   9X +   6Y =   2898

-10X + -6Y  = -3134

-X = -236

X =  236 --> so the price of the PB is 236 pennies or $2.36

Plugging into the second equation as the numbers are a bit smaller,

5X + 3Y = 1567

5(236) + 3Y = 1567

1180 + 3Y = 1567

3Y = 387

Y = 129. So the price of the jelly is 129 pennies or $1.29.

Now we check:  4 x $1.29 + 6*2.36 = $19.32

                       3 x $1.29 + 5 x 2.36 = $15.37

The answers are verified and highlighted in bold.

6X + 4Y = 1932  <--- price is in pennies

5X + 3Y = 1567 <--- price in pennies