(a) Let the percentage of _{17}X ^{37} is p

Percentage of _{17}X ^{35} = (100 – p)

Average atomic weight = 35.5

Therefore

35.5 = 37p + 35(100 − p) /100

3550 = 37p + 3500 − 35p

3550 – 3500 = 37p - 35p

2p = 50 ⇒ p = 25%

Therefore, sample of _{17}X ^{37} is 25% and _{17}X ^{35} will be 100 – 25 = 75%

(b) Cesium 137 – Used to treat cancerous tumors. Calcium 47 – It is an important aid for biomedical researchers studying the cellular functions