1) 15c + 3c - 12 = 78;

15c + 3c = 78 + 12;

18c = 90;

c = 5;

2) (6y + 14): 2 = 40 - 15;

6y + 14 = 25 * 2;

6y + 14 = 50;

6y = 50 - 14 ;

6y = 36;

y = 6.