



 
Hi, Thus is an ambiguous statement and for exactly mathematicians and people who use mathematics have a selfimposed rule. The rule is that multiplication is always performed before addition. This selfimposed rule is somewhat more involved but for your example this is all we need. The rule is used so that there is no ambiguity, everyone knows what $20 + 30\times0 + 1$ means. With this rule when you see the expression $20 + 30\times0 + 1$ you should see the multiplication symbol first and the multiplication is $30 \times 0$ which is $0$ so \[ 20 + 30\times0 + 1= 20 + 0 + 1.\] I hope this helps,  


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