Hi,

Thus is an ambiguous statement and for exactly mathematicians and people who use mathematics have a self-imposed rule. The rule is that multiplication is always performed before addition. This self-imposed 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,
Penny