Metabolic acidosis because the arterial pH goes in the same direction as the bicarb and pCO2 (i.e. both pH and bicarb/pCO2 are decreased from normal); in primary respiratory acidosis/alkalosis the arterial pH goes in the opposite direction as the bicarb and pCO2.
Once you know that it is a primary metabolic acidosis, you have to check for concomitant respiratory disorders. Do this with Winter's formula:
expected pCO2 = 1.5(HCO3) + 8 +/- 2
so... expected pCO2 = 1.5(11) + 8 +/- 2 --> pCO2 = 24.5 +/- 2 = expected pCO2 is between 22.5-26.5, therefore, 23 is in the expected range, no concomitant respiratory process