Answer:
1/5
Step-by-step explanation:
Refer to the image for the region. I've chosen to "scan" the region horizontally for convenience sake, so x varies for values between the green and the red line, and y varies from 0 to 1.
The two lines have equations [tex]x=7-6y[/tex] (red line) and [tex]x=7-7y[/tex] (green line). Since we're integrating first with respect to x, it's easier to write the equation like that and not as [tex]y=mx+q[/tex] since they will become our new limits of integration
Our double integral will become
[tex]\int \limits_0^1 \ \ \int \limits_{7-7y}^{7-6y}y^3dxdy = \int \limits_0^1 y^3x|\limits_{7-7y}^{7-6y} dy =\\\int \limits_0^1 y^3[(7-6y)-(7-7y)]dy = \int \limits_0^1y^3(y)dy =\\\int \limits_0^1 y^4dy =\frac15y^5|\limits_0^1=\frac15[/tex]
