Differenciate x^6 with respect to 1/√x

Asalesperson earns $320 per week plus 8% of her weekly sales. the expression representing her earnings is 320 + 0.08x. which of the following describes the sales necessary for the salesperson to earn at least $1000 in the one week?

Acredit card advertises an annual interest rate of 23%. what is the equivalent monthly interest rate?

Which shows the correct substitution of the values a, b and c from the equation 1=-2x+3x^2+1