You know the probabilities of red and blue. How can you use $1 - (P(\text{red}) + P(\text{blue}))$ to get the probability of green?

Once you know the probability of green, how do you use the total of 300 beads to find how many of them are green?

In Desmos, type the expression 300*(1 - 0.35 - 0.40) on a new line. The value that Desmos outputs is the number of green beads in the jar.

The jar has only red, blue, and green beads, so the probabilities of picking each color must add up to 1 (or 100%).

Let $P(\text{green})$ be the probability of selecting a green bead. Then:

You are given $P(\text{red}) = 0.35$ and $P(\text{blue}) = 0.40$. Plug these into the equation to solve for $P(\text{green})$.

Substitute the known probabilities into the equation:

Add the red and blue probabilities:

Now subtract $0.75$ from both sides to get the probability of green:

So the probability of picking a green bead is $0.25$ (or $25\%$).

A probability of $0.25$ means that $25\%$ of the 300 beads are green. To find how many beads that is, multiply the total number of beads by this probability:

Compute the product:

So there are 75 green beads in the jar, which corresponds to answer choice C) 75.