Assuming the 6 is the entire value on the right and it wasn't cut off...
Perimeter: Add up all the side lenghts, as if you were walking around the rectangle.
perimeter = top + right side + bottom + left side
= 3x+4 + 6 + 3x+4 + 6
= 6x + 20
Area: Multiply the length times the width.
area = top • right side
= (3x+4) • 6
= 18x + 24 using distribution
