R2 and R3 are both connected to the same start and end point in the circuit, so are in parallel. Calculate their combined resistance using the 1/R rule, and then treat those two as a resistor in series with R1.
R2 and R3 are both connected to the same start and end point in the circuit, so are in parallel. Calculate their combined resistance using the 1/R rule, and then treat those two as a resistor in series with R1.
Well the two black dots in the circuit mark the point at which two paths diverge and then come together. In each of these paths, there is a resistor. Therefore they are in parallel.