To find $m\angle RSU$, let's analyze the given image and the angles provided:

1. $\angle RST = 64^\circ$
2. $\angle TSU = 60^\circ$

Since $\angle RSU$ is the sum of $\angle RST$ and $\angle TSU$, we add these two angles:

$m\angle RSU = m\angle RST + m\angle TSU = 64^\circ + 60^\circ = 124^\circ$

Therefore, $m\angle RSU = 124^\circ$.

Would you like a detailed step-by-step explanation or have any other questions?

Here are some related questions:

1. How do you find the measure of an unknown angle in a triangle?
2. What are the properties of adjacent angles?
3. How can you find angles formed by intersecting lines?
4. How do complementary and supplementary angles differ?
5. What are the basic rules for solving problems involving angle addition?

Tip: When working with angle problems, carefully identify the relationships between angles, such as complementary, supplementary, or adjacent, to solve the problem accurately.