Answer:
2( m + n ) + 7
Step-by-step explanation:
(m + n + 3) + (m + n + 4) Open the brackets by multiplying by +1
= m + n + 3 + m + n + 4 Collect like terms
= m + m + n + n + 3 + 4
= 2m + 2n + 7
= 2( m + n ) + 7
