F(x)= 2x+4/3 using the inverse function x=6 how do you solve this ?

Ineed asap.i cant understand this question i need someone to me right away

The graph shows the distance y, in inches, a pendulum moves to the right (positive displacement) and to the left (negative displacement), for a given number of seconds x. how many seconds are required for the pendulum to move from its resting position and return? enter your answer in the box.

Jacks bank statement shows an account balance of -$25.50. which describes the magnitude, of size, of the debt in dollars