17 * (c-3) - 36=19 + (c-2) * 12

Найдем корни.

17 * (c - 3) - 36 = 19 + (c - 2) * 12;

17 * с - 17 * 3 - 36 = 19 + 12 * с - 2 * 12;

17 * c - 51 - 36 = 19 + 12 * c - 24;

Приведем подобные.

17 * c - 87 = 12 * c - 5;

17 * c - 12 * c = - 5 + 87;

5 * c = - 82;

c = - 82/5;

c = - 10 - 6 - 0.4;

c = - 16.4.