Someone help if right will mark brainiest

Add the fractions, and simply the result to lowest terms. 2/3 + 2/7= ?

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.