Answer:
16. r = 20
t = 48
17. a = 104
b = 175
19.

7.2 = 7.2
20.

1.5 = 1.5
21.

3 = 3
22.

219 grams of peanuts
23.

50 milligrams of medication
Explanation:
16.

8 · 4 = 32
5 · 4 = 20
r = 20
5 · 6 = 30
8 · 6 = 48
t = 48
17.

Here is a different method.

52 · 2 = 104
a = 104
350 ÷ 2 = 175
b = 175
22.

8 · y = 3 · 584
8y = 1752
8y ÷ 8 = 1752 ÷ 8
y = 219
23.

y · 80 = 200 · 20
80y = 4000
80y ÷ 80 = 4000 ÷ 80
y = 50