Answer:
15 + 5x
Explanation:
8x + 1 + 7x + 4
All that you need to do is combine like terms which means that you need to put together (either add or subtract) the numbers that are similar...so the numbers with the numbers, and the variables with the variables...
8x + 7x and 1 + 4
15x + 5
And you cannot do anything else because it is in its simplest form.
Hope this helped!
Have a supercalifragilisticexpialidocious day!