#### Answer

$15a+26$

#### Work Step by Step

Commutative properties: $a+b=b+a,\qquad ab=ba$
Associative properties:$ a+(b+c)=(a+b)+c,\qquad a(bc)=(ab)c$
Distributive property: $\quad A(x+y)=Ax+Ay$
Simplifying Algebraic Expressions:
1. Use distributive property to remove parentheses
2, Rearrange terms and group like terms using the commutative and associative properties.
3. Combine terms by combining the coefficients of the terms and keeping the same variable factor.
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$ 13a+15+2a+11=\qquad$
...commutative property: $15$ and $2a$ can change places
$13a+2a+15+11=$
...associative property: select groups of like terms
$=(13a+2a)+(15+11)$
... combine like terms,
= $15a+26$