I beleive the answer is C
Answer:
x = 10
Step-by-step explanation:
1) Subtract x from both sides.
4x − x = 30
2) Simplify 4−x to 3x
3x = 30
3) Divide both sides by 3
x = 
4) Simplify
to 10
x = 10
The next term in the sequence is 90. Each term is 18 less than the previous, and 108-18 is 90.
If the function is:
y=a cos( bx+c), or y=a sin(x+c)
then the period is T= 2π/b and if T=2:
2=2π/b
b=2π/2=π
Answer: B) y=3 cos πx