California Baptist University Probability Question

Question Description

I need support with this Mathematics question so I can learn better.

In a game of roulette, there are 38 slots for a ball to drop
into when it is rolled around the rim of a revolving wheel: 18 red, 18 black,
and 2 green. What is the probability that the first time a ball drops into the
red slot is on the 8th trial (in other words, suppose you are betting on red
every time-what is the probability of losing 7 straight times before you win
the first time)?