Check out this webpage for help understanding stoichimetry!

https://chemfiesta.wordpress.com/2015/02/02/the-magic-of-stoichiometry/

Also, here are some practice worksheets: Go to this website and scroll down about half-way down the page and you will see some links to stoichiometry pages.

https://chemfiesta.wordpress.com/2015/03/26/chemical-equations-worksheets/