3x+6=30 what is the value of x​

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.

Iwant to know what 3g+5h+4g-2h is my teacher is too selfish to tell us

Can any one me with the answers to these questions asap?