To add these fractions, we first need to find a common denominator for each pair of fractions.

For the first pair, 19/84 and 15/90, the least common multiple of 84 and 90 is 840. We can rewrite the fractions with this common denominator:

19/84 = (1910)/(8410) = 190/840
15/90 = (159)/(909) = 135/840

Now, we can add the fractions:

190/840 + 135/840 = (190+135)/840 = 325/840

For the second pair, 3/49 and 62/245, the least common multiple of 49 and 245 is 1225. We can rewrite the fractions with this common denominator:

3/49 = (325)/(4925) = 75/1225
62/245 = (625)/(2455) = 310/1225

Now, we can add the fractions:

75/1225 + 310/1225 = (75+310)/1225 = 385/1225

Therefore, 19/84 + 15/90 = 325/840 and 3/49 + 62/245 = 385/1225.