What are the answers to the following.

What is sin 7x/4 ? i need on this urgent trig

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

Write a function for a rotation 90 degrees counter clockwise about the origin, point 0