Answer
$11y+3$
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: $\quad A(x+y)=Ax+Ay$
---
$ 5y+3+6y=\qquad$
...commutative property: $3$ and $6y$ can change places
$=5y+6y+3=$
...associative property: we can add any pair we like, first
$=(5y+6y)+3$
... recognize the distribution
$=y(5+6)+3$
... parentheses first,
$=y\cdot 11+3$
... multiplication is commutative, y and 11 can change places
= $11y+3$
