Answer:
first make it so the denominator is the same on bothers sides. a common denominator for both is 6 so
Chrystelle mom: 1 2/3 taller. multiply the fraction by 2/2 so 1 4/6
chrystelle: 3 1/2 feet tall. multiply the fraction by 3/3 so 3 3/6
now just add to figure out so
3 3/6 + 1 4/6 = 4 7/6 which simplifies down to 5 1/6
so chrystelles mom is 5 1/6 feet tall