$$ACC = \frac{TP + TN}{TP+TN+FP+FN} \tag{1}$$

ACC = (20 + 50) / 100 = 70%

$$P = \frac{TP}{TP + FP} \tag{2}$$
P = 20 / (20 + 30) = 40%

$$R = \frac{TP}{TP + FN} \tag{3}$$
R = 20 / 20 = 100%