pt is the Distribution function in R:
df = degree of freedom (n1+n2-2)
q = Value of Test Statistic (Even if the Test Statistics value is -ve we will take the absolute value (+ve values only))
//pt (q, df, lower.tail =FALSE)
pt(3.102, 18, lower.tail=FALSE)*2
As per the Pvalue we need to compute 2 side so multiply by 2, if the T distribution is Symmetric
//qt(p,df)
qt(0.975,18) or qt(0.025.18, lower.tail=FALSE)