3. (10 points) Divide students into 35 groups, each with 3 people. Among them, there are 10 groups with only 1 boy, 19 groups with no less than 2 boys, and the number of groups with 3 boys is twice the number of groups with 3 girls. Then the number of boys is $\qquad$ people.
【Analysis】There are four cases in total: (1) 3 girls, (2) 2 girls 1 boy, (3) 1 girl 2 boys, (4) 3 boys. According to the fact that there are 10 groups with only 1 boy, we can deduce that there are 10 groups in case (2). For the 19 groups with no less than 2 boys, cases (3) and (4) together have 19 groups, which means case (1) has $35-19-10=6$ (groups). Since the number of groups with 3 boys is twice the number of groups with 3 girls, case (4) has $6 \times 2=12$ (groups).
Case (3) has $19-12=7$ (groups). Adding up the number of boys in each group will give us the solution.

【Solution】Solution: There are four cases in total: (1) 3 girls, (2) 2 girls 1 boy, (3) 1 girl 2 boys, (4) 3 boys.

According to the fact that there are 10 groups with only 1 boy, we can deduce that there are 10 groups in case (2), with $10 \times 1=10$ (boys). For the 19 groups with no less than 2 boys, cases (3) and (4) together have 19 groups,

which means case (1) has $35-19-10=6$ (groups), with no boys in these 6 groups;
Since the number of groups with 3 boys is twice the number of groups with 3 girls,
case (4) has $6 \times 2=12$ (groups), with $12 \times 3=36$ (boys)
Case (3) has $19-12=7$ (groups), with $7 \times 2=14$ (boys)

The total number of boys is $10+36+14=60$ (boys)
Answer: There are 60 boys.
The answer is: 60.