Dishwasher a machine that washes dishes.

My parents are....at..... work now.

Áp dụng tc dãy tỉ số bằng nhau ta có

\(\frac{a+b+c}{a+b-c}=\frac{a-b+c}{a-b-c}=\frac{a+b+c-a+b-c}{a+b-c-a+b+c}=\frac{2b}{2b}=1\)

\(\Rightarrow a+b+c=a+b-c\)

\(\Rightarrow a+b+c-a-b+c=0\)

\(\Rightarrow2c=0\)

\(\Rightarrow c=0\)