Can someone me with this question?

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?

Write as a product: ac^2–ad+c^3–cd–bc^2+bd

Consider the sequence below. 3 , 1 , 1/3 , 1/9 , select the explicit function which defines the sequence.