Note that 21 = 3*7, and that 35 = 5*7. Thus, 7 is common to 21 and 35. Next, note that w11 and w7 should be rewritten as w^11 (w to the 11th power), and w7 as w^7.
Then we have:
3*7*w^11 + 5*7*w^7.
The common factors 7 and w^7 can be taken out now:
7w^7*(3w^4 + 5) (answer)
