Answer: 7.56 ohms
Step-by-step answer:
First find total R in the parallel
1/R=(1/R1)+(1/R2)
1/R= (1/1.9)+(1/3)
1/R=4.9/5.7
R= 5.7/4.9
R=1.16 ohms
The 2 resistors and our 1 new one are in series so add to get total
4.5+1.9+1.16= 7.56 ohms
Total resistance from A to C is 7.56 ohms