The ornamental design for a backpack with detachabledoodleboard, as shown and described.
FIG. 1 is a front, left side perspective view of a backpack with detachable doodle board, showing my new design;
FIG. 2 is a bottom, left side perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a front, left side perspective view of the backpack with detachable doodle board which the backpack and the front pocket board are in separate state.
The dot lines depict stitching of the backpack with detachable doodle board that do not form part of the claimed design.