Fond the degree measure of each angle in the triangle

Note that the sum of the angles in a triangle is always 180 degrees.
So it follows that :
[tex]\angle F+\angle G+\angle H=180[/tex]The triangle has a right angle at G, and a right angle measures 90 degrees.
angle F = 4x + 15
and
angle H = 3x + 12
Substitute the angle values to the formula and solve the value of x :
[tex]\begin{gathered} \angle F+\angle G+\angle H=180 \\ (4x+15)+(90)+(3x+12)=180 \\ 7x+117=180 \\ 7x=180-117 \\ 7x=63 \\ x=\frac{63}{7}=9 \end{gathered}[/tex]Now we have the value of x, substitute this value to the angles.
[tex]\begin{gathered} F=4x+15=4(9)+15=51 \\ H=3x+12=3(9)+12=39 \end{gathered}[/tex]Therefore, the angles are :
F = 51 degrees
G = 90 degrees
H = 39 degrees