Explain what the expression (5903+1250) x6 means

You are multiplying the sum of 5903 and 1250 by six.

So, because the 5903 + 1250 are parentheses, you want to treat like it's own equation first.

5903 + 1250 = 7153.

Now your equation looks like (7153) * 6

or 7153 * 6

the answer to this equation is 42918

(5903+1250) * 6

add the numbers in parenthesis then multiply it by 6 you should get 13,403