I've always been surprised by the number of students taking high school and college math courses who have forgotten basic concepts they learned in grammar school. Adding and subtracting fractions is a surprising top contender for this prize. Another one is order of operations:
The graphic above is supposed to remind you of the following order to arithmetic calculations:
When you think you understand PEMDAS, try the following practice example:
When you're ready to check your answer (to three decimal places), look down at the bottom left corner of this page.
There are many places one can get help with basic math. One online tutorial to check out has been developed by the Goodwill Community Foundation.
Answer = -0.270