3. (7 points) Guangming Primary School planted a total of 120 poplar and willow trees this spring, among which the number of poplar trees is 10 less than that of willow trees. The number of poplar trees planted is $\qquad$.

【Solution】Solution: Let there be $x$ poplar trees, then there will be $10+x$ willow trees. According to the problem, we have:
$$
\begin{array}{l}
10+x+x=120 \\
2 x=110 \\
x=55
\end{array}
$$

There are 55 poplar trees, so the answer is 55.