There are $30$ questions in a multiple-choice test. $A$ student gets $1$ mark for each unattempted question,$0$ mark for each wrong answer,and $4$ marks for each correct answer. If a student answered $x$ questions correctly and scored $60$,then the number of possible values of $x$ is:

If $\sqrt{9x^2+6x+1} < (2-x)$,then:

In an experiment,a solution of hydrochloric acid is to be kept between $30^{\circ} \text{C}$ and $35^{\circ} \text{C}$. What is the range of temperature in degree Fahrenheit if the conversion formula is given by $C = \frac{5}{9}(F - 32)$,where $C$ and $F$ represent temperature in degree Celsius and degree Fahrenheit,respectively?

$A$ solution of $8 \%$ boric acid is to be diluted by adding a $2 \%$ boric acid solution to it. The resulting mixture is to be more than $4 \%$ but less than $6 \%$ boric acid. If we have $640$ litres of the $8 \%$ solution,how many litres of the $2 \%$ solution will have to be added?

Let $m, n$ be real numbers such that $0 \leq m \leq \sqrt{3}$ and $-\sqrt{3} \leq n \leq 0$. The minimum possible area of the region of the plane consisting of points $(x, y)$ satisfying the inequalities $y \geq 0$,$y - 3 \leq mx$,and $y - 3 \leq nx$ is