The incorrect calculation may be made correct bay increasing one of these number by

Toán Tiếng Anh:
Question 1:
​The incorrect calculation: 2$\times$3$+$6$\times$4=42 may be made correct bay increasing one of these number by 2.Wich number should it be?
Question 2:
James buys 5 Harry Potter books at $200,25 each.What is the total cost?
Question 3:
Charlie buys two pairs of shoes for $15,75 each.He gives the clerk $50,00.How much change should Charlie receive?
Question 4:
The value of:2,5$\times$4,15$+$7,623 is $...$
Question 5:
If you can ride 7,35km in 15 minutes then how far can you ride in 2 hours?