resistance INCREASED by 50%....therefore, if normal resistance is VR, you have to multiply the normal VR by 150% (or 1.5 which is (3/2)). CO=(P/VR) but the question stem states pressure doubles (therefore P is now 2P) and resistance increases by 50% (therefore VR is now (3/2)VR) so your new equation is CO=(2P/((3/2)VR)).....when you divide, you multiply by the reciprocal...CO=(2P)((2/3)VR) so your new coefficient of the (P/VR) is (4/3). The coefficient of the original was 1 which is equal to (3/3). To go from (3/3) to (4/3) you have to increase by (1/3). Let me know if you have any other questions.
