YSK the US Navy has a set of manuals to teach basic math all the way up to pre-Calculus and statistics

The Navy has four manuals used to teach those with very minimal education basic math.

To get a sense of the education level assumed, NAVEDTRA 14139 starts with a review of addition, subtraction, and multiplication (assuming that you've seen these things before but reminding you how to do them), the first full unit that is not a review is on fractions.

• NAVEDTRA 14139 Mathematics Basic Math and Algebra - 13.8 MB
• NAVEDTRA 14140 Mathematics Trigonometry - 8.39 MB
• NAVEDTRA 14141 Mathematics Pre Calculus and Introduction to Probability - 10.4 MB
• NAVEDTRA 14142 Mathematics Introduction to Statistics Number Systems and Boolean Algebra - 6.61 MB