$\begin{array}{l} a) - 7x + 10 \ge 0\\ \Leftrightarrow 7x \le 10 \Leftrightarrow x \le \dfrac{{10}}{7} \Rightarrow S = \left( { - \infty ;\dfrac{{10}}{7}} \right]\\ b) - {x^2} + 7x - 12 > 0\\ \Leftrightarrow {x^2} - 7x + 12 < 0\\ \Leftrightarrow \left( {x - 4} \right)\left( {x - 3} \right) < 0 \Leftrightarrow S = \left( {3;4} \right) \end{array}$