Math 1. When Xiao careless calculates 30 +× 4, he first calculates addition and then multiplication, and the result is 400. What is the correct result of this question?
Because he calculates addition first and then multiplication, the formula of 30 +×× 4 is 4*(30+□)=400.
30+□= 100
□=70
You can keep asking me if you don't understand.