For n1=22, the degrees of freedom (DOF)=21 and for n2=15, DOF=14. We are specifically testing μ1<μ, where μ1 is presumably the sample mean for each sample, or their average. This is a one-tailed t-test, with the significance level α=0.05, a confidence level of 95%. (A 2-tailed test would apply if we were testing μ1≠μ, which is an "either side"-of-the-mean test. We are only interested in the left-side of the mean, hence a 1-tailed test.)
The individual critical values from tables would be 1.761 (DOF=14) and 1.721 (DOF=21).
The combined DOF is 22+15-2=35 or the sum of the individual DOFs=21+14=35. This gives us a critical value of 1.691 approx.