6. Task 5 № 12872: Monthly phone bill is 680 rubles per month. How much will the bill be if it increases by 5%?

First, calculate the increase amount: $$5\% \text{ of } 680 = 0.05 * 680 = 34$$ Next, add the increase to the original amount: $$680 + 34 = 714$$ So, the new monthly bill will be **714 rubles**.