According to the graph we have:
1. If the lines A and B cut by the secant D are parallel, then the collateral angles are supplementary, i.e. add up to 180°. In this case:
[tex](3x+7)+(4x+5)=180[/tex]2. Solve for x:
[tex]\begin{gathered} 3x+7+4x+5=180 \\ 7x+12=180 \\ 7x+12-12=180-12 \\ 7x=168 \\ \frac{7x}{7}=\frac{168}{7} \\ x=24 \end{gathered}[/tex]Answer: x = 24
3. Angle 6 corresponds to angle 3x + 7 so they are equal. So:
[tex]\angle6=3x+7[/tex]Where: x = 24
Substitute the value:
[tex]\angle6=3(24)+7=72+7=79[/tex]Answer: <6 = 79°