Time running: r
Time swimming: s
r/s = 1.5/0.75 = 2 ⇒ r = 2s
r + s > 6
2s + s > 6
3s > 6
s > 2
Possible times:
r = 2s and s>2
Draw the lines s=2 and r=2s
s=2 is a vertical line (parallel to r axis) and the set of solutions for r >2 is all the area further to the righ of s = 2
r = 2s is a leaned line.
The solutions are all the points that belong to the line r =2s and are furtther to the right of s=2, but below a feasible s (beacause he cannot train more than certain number of hours daily)