Jenny buys an 18'sandwich. Demi gets 1/2 the amount the Jenny gets. Joel gets 3/4 the amount Jenny gets. How much does Jenny get? Please explain.

I assume you meant 18 inches ( ' usually is the symbol for feet if I recall the imperial measure system)

jenny --> x inches
Demi--> half of that or x/2 inches
Joel --> gets 3/4 of Jenny's or 3x/4

x + x/2 + 3x/4 = 18
times 4

4x + 2x + 3x = 72
9x = 72
x = 8

Jenny gets 8 inches.

check:
Jenny -- 8
Demi --- 4
Joel ---- 6
total = 8+4+6 =18

To find out how much Jenny gets, we need to evaluate the given fractions. Let's break it down step by step:

1) Jenny buys an 18-inch sandwich. Since this is the whole amount, we can say Jenny gets 1 whole sandwich or 1/1.

2) Demi gets 1/2 the amount Jenny gets. To find out how much Demi gets, we multiply Jenny's amount by 1/2:

Demi's amount = Jenny's amount x 1/2
Demi's amount = 1 x 1/2
Demi's amount = 1/2

Therefore, Demi gets 1/2 of the 18-inch sandwich, which is 9 inches.

3) Joel gets 3/4 the amount Jenny gets. Similar to Demi, we multiply Jenny's amount by 3/4:

Joel's amount = Jenny's amount x 3/4
Joel's amount = 1 x 3/4
Joel's amount = 3/4

Therefore, Joel gets 3/4 of the 18-inch sandwich. To find out the exact amount, we need to multiply 3/4 by 18:

Joel's amount = 3/4 x 18
Joel's amount = 54/4
Joel's amount = 13.5 inches

Therefore, Joel gets 13.5 inches of the 18-inch sandwich.

In summary:
- Jenny gets the whole 18-inch sandwich (18 inches).
- Demi gets 1/2 of the 18-inch sandwich (9 inches).
- Joel gets 3/4 of the 18-inch sandwich (13.5 inches).