9. นักศึกษาห้องหนึ่งมี 45 คน เป็นนักศึกษาชาย \( \frac{2}{2} \) ของนักศึกษาทั้งหมด ห้องนี้มีนักศึกษาชาย 3 ทั้งหมดกี่คน ก. 15 ข. 20 ค. 25 ง. 30

An unknown compound has the following chemical formula: where \( x \) stands for a whole number. Measurements also show that a certain sample of the unknown compound contains 9.6 mol of nitrogen and 9.3 mol of oxygen. Write the complete chemical formula for the unknown compound.

A car accelerates at a rate of \( 8.8 \mathrm{~m} / \mathrm{s}^{2} \) with a force from the tires of 19,976 What is the mass of the car?

Classify the given function as a polynomial function, rational function, or root function, and then fi \( f(x)=\sqrt{x^{2}-3 x-18} \)

Consider the following function. \[ f(x)=\left\{\begin{array}{lll}x^{2}+x & \text { if } \quad x<-3 \\ 6 & \text { if } & x=-3 \\ 2 x-1 & \text { if } & x>-3\end{array}\right. \] Evaluate the given limits. If a limit does not exist, enter DNE. (a) \( \lim _{x \rightarrow-3^{-}} f(x)=\square \) (b) \( \lim _{x \rightarrow-3^{+}} f(x)=\square \) (c) \( \lim _{x \rightarrow-3} f(x)=\square \)

Simplify each side of the equation when possible. Then solve the equation and check the solution \( 4+\mathrm{b}=-20-8 \)