If you've worked with the sound chart, you can visualize how "diez" sounds exactly like English "the yes" - but said very rapidly and slurred together.

Note also that the next 5 numbers end with -ce.

16 through 19 have 2 spellings: choose whichever one you like, but stick to one pattern for simplicity's sake.

Also focus on the fact that 16 is the first number to use a compound of diez + another number.

Most English speakers lose this at some point, and try to start the diez y before 16.

Listen to & repeat the numbers a few times, then count hot air balloons, starting from 0 to as high as you can. You should be able to keep up with each one and not get stuck before the next one shows up.

Cuando la temperatura está entre 10 y 19 grados Fahrenheit, hace mucho frío.