A right angle measures $90^\circ$. If $\angle C$ is right and $\angle A$ is $35^\circ$, write an equation for $\angle A + \angle B + \angle C$ adding up to $180^\circ$.

From your equation, combine the known angles into a single number and then solve for $\angle B$ by subtracting from $180^\circ$.

In the expression line, type 180 - 90 - 35 and look at the numerical result; this value is the measure of $\angle B$ in degrees.

For any triangle, the measures of the three interior angles always add up to $180^\circ$.

So in triangle $ABC$:

You are told that $\angle C$ is a right angle, so $\angle C = 90^\circ$, and $\angle A = 35^\circ$.

Substitute these into the angle-sum equation:

Combine the known angles:

Solve $125^\circ + \angle B = 180^\circ$ by subtracting $125^\circ$ from both sides:

So the measure of $\angle B$ is $55^\circ$, which corresponds to choice C.