Expand and simplify 2y+3y(5y+3)

Following the laws of BIDMAS, the bracket needs to be multiplied first (instead of adding 2y and 3y first):

2y + 15y² + 9y

Simplify by addition of the y's:

15y² + 11y

Optional: simplify further by grouping y's:

y(15y + 11)