Jamel is asked to create triangles using three of four given sticks. the sticks measure 3 in., 6 in., 7 in., and 8 in. he creates these 4 triangles. how many of his triangles are obtuse?

3 triangles 

Explanation:
Before, we begin, you need to remember the following:
We can determine the type of triangle based on its three sides as follows:
(longest side)² = (first short side)² + (second short side)² > right Δ
(longest side)² > (first short side)² + (second short side)² > obtuse Δ
(longest side)² < (first short side)² + (second short side)² > acute Δ

Now, let's check our question here:
There are 4 possible triangles that could be formed. They are listed as follows:
A) 3, 6 and 7 in
B) 3, 6 and 8 in
C) 3, 7 and 8 in
D) 6, 7 and 8 in

Let's apply the check to know the type of each triangle:
1- Triangle A:
(7)² = 49
(3)² = 9
(6)² = 36
49 > 9 + 36
49 > 45
This triangle is obtuse

2- Triangle B:
(8)² = 64
(3)² = 9
(6)² = 36
64 > 9 + 36
64 > 45
This triangle is obtuse

3- Triangle C:
(8)² = 64
(7)² = 49
(3)² = 9
64 > 49 + 9
64 > 58
This triangle is obtuse

4- Triangle D:
(8)² = 64
(6)² = 36
(7)² = 49
64 < 49 + 36
64 < 85
This triangle is acute

Hope this helps :)