To simplify the expression we need to combine all the terms that have the same letter. When we do that we have to sum the numerical parts while mantaining the literal parts. This is done step-by-step below:
[tex]4r\text{ + (7j) + 4r}[/tex][tex]4r+4r+7j[/tex][tex]8r+7j[/tex]The simplified expression is: 8r + 7j. This is because we can't sum two monomials with different literal parts.