You are going to read a dialogue between a mum and her daughter. Read sentences A-F. What is the dialogue about? A But, Mum, I'm so busy at the moment. В What have I done now?

(c-3)*12=20-4*(c+2)   проверяем (3-3)*12=20-4*(3+2)
12с-36=20-4с-8           0=20-20   
12с+4с=12+36          0=0
16с=48
с=3

(с-3)*12=20-4*(с+2)
12с-36=20-4с-8
12с+4с=36+20-8
16с=48
с=3