We are asked to find the missing angle in each of the given triangles.
Recall the fact that the sum of interior angles of a triangle must be equal to 180°.
7)
[tex]45\degree+35\degree+x=180\degree[/tex]
Let us solve the above equation for the unknown angle x.
[tex]\begin{gathered} 45\degree+35\degree+x=180\degree \\ 80\degree+x=180\degree \\ x=180\degree-80\degree \\ x=100\degree \end{gathered}[/tex]
Therefore, the missing angle is 100°
8)
Similarly, sum the angles and equate them to 180°
[tex]\begin{gathered} 100\degree+x+40\degree=180\degree \\ 140\degree+x=180\degree \\ x=180\degree-140\degree \\ x=40\degree \end{gathered}[/tex]
Therefore, the missing angle is 40°
9)
Similarly, sum the angles and equate them to 180°
[tex]\begin{gathered} x+90\degree+16\degree=180\degree \\ x+106\degree=180\degree \\ x=180\degree-106\degree \\ x=74\degree \end{gathered}[/tex]
Therefore, the missing angle is 74°
