Answer:
When we want solve expression mentally, that is, without writing down anything, a nice way is to separate number in simpler expressions, like tens for example.
So, in first place we could multiply 7 x 50, which involves a number expressed in tens, this product would be 350, then we multiply 7 x 3, which is 21, at the end, we sum both results 350 + 21 = 371. Therefore, the product is 371.
If we want to write an expression, it would be
7 x 50 + 7 x 3 = 350 + 21 = 371
