Answer :
21- 7t + 3r - rt
Group:
(21- 7t) + (3r - rt)
Factor out the common factors:
7 (3 - t) + r (3 - t)
Use the distributive property:
(3 - t) (7 + r)
Group:
(21- 7t) + (3r - rt)
Factor out the common factors:
7 (3 - t) + r (3 - t)
Use the distributive property:
(3 - t) (7 + r)
