Answer
$75$
Work Step by Step
$$\eqalign{
& \mathop {\lim }\limits_{x \to 5} \left( {4{x^2} - 5x} \right) \cr
& {\text{Suppose that }}c{\text{ is a constant and the limits }} \cr
& {\text{ }}\mathop {\lim }\limits_{x \to a} f\left( x \right){\text{ and }}\mathop {\lim }\limits_{x \to a} g\left( x \right) \cr
& \cr
& {\text{Use the Difference Law }} \cr
& \mathop {\lim }\limits_{x \to a} \left[ {f\left( x \right) - g\left( x \right)} \right] = \mathop {\lim }\limits_{x \to a} f\left( x \right) - \mathop {\lim }\limits_{x \to a} g\left( x \right) \cr
& \mathop {\lim }\limits_{x \to 5} \left( {4{x^2} - 5x} \right) = \mathop {\lim }\limits_{x \to 5} \left( {4{x^2}} \right) - \mathop {\lim }\limits_{x \to 5} 5x \cr
& \cr
& {\text{Use the Constant Multiple Law }} \cr
& \mathop {\lim }\limits_{x \to a} \left[ {cf\left( x \right)} \right] = c\mathop {\lim }\limits_{x \to a} f\left( x \right) \cr
& \mathop {\lim }\limits_{x \to 5} \left( {4{x^2}} \right) - \mathop {\lim }\limits_{x \to 5} 5x \cr
& = 4\mathop {\lim }\limits_{x \to 5} \left( {{x^2}} \right) - 5\mathop {\lim }\limits_{x \to 5} \left( x \right) \cr
& \cr
& {\text{Use The power Law }}\mathop {\lim }\limits_{x \to a} {x^n} = {a^n}{\text{, }}n{\text{ is a positive integer }} \cr
& {\text{and the law}}\mathop {\lim }\limits_{x \to a} x = a,{\text{ then}} \cr
& 4\mathop {\lim }\limits_{x \to 5} \left( {{x^2}} \right) - 5\mathop {\lim }\limits_{x \to 5} \left( x \right) = 4{\left( 5 \right)^2} - 5\left( 5 \right) \cr
& {\text{Simplifying}} \cr
& = 4\left( {25} \right) - 25 \cr
& = 75 \cr} $$
