In a group of $70$ people,$37$ like coffee,$52$ like tea and each person likes at least one of the two drinks. How many people like both coffee and tea?

Each set $X_r$ contains $5$ elements and each set $Y_r$ contains $4$ elements. If $\bigcup_{r=1}^{24} X_r = S = \bigcup_{r=1}^{n} Y_r$,and each element of set $S$ belongs to exactly $10$ of the $X_r$'s and to exactly $6$ of the $Y_r$'s,then find the value of $n$.

Let $S = \{(x, y, z) : x, y, z \in \mathbb{Z}, x + 2y + 3z = 42, x, y, z \geq 0\}$. Find the number of elements in $S$.

In a certain town,$25\%$ of families own a phone,$15\%$ own a car,and $65\%$ of families own neither a phone nor a car. If $2000$ families own both a car and a phone,consider the following statements:
$1$. $10\%$ of families own both a car and a phone.
$2$. $35\%$ of families own either a car or a phone.
$3$. $40,000$ families live in the town.
Which of the above statements are correct?

$a, b, c, d, e, f, g, h$ are distinct elements in the set $\{-7, -5, -3, -2, 2, 4, 6, 13\}$. The minimum value of $(a+b+c+d)^2+(e+f+g+h)^2$ is

Let $\bigcup_{i=1}^{50} X_{i} = \bigcup_{i=1}^{n} Y_{i} = T$,where each $X_{i}$ contains $10$ elements and each $Y_{i}$ contains $5$ elements. If each element of the set $T$ is an element of exactly $20$ of the sets $X_{i}$ and exactly $6$ of the sets $Y_{i}$,then $n$ is equal to: