William W. answered 09/21/19
Math and science made easy - learn from a retired engineer
First, define the variables. Let's let W be "the previous weight of the individual" since that is what we are looking for.
If the person loses 28 pounds then their new weight is W - 28. The problem says that their new weight is 98 pounds more than 1/3 their previous weight. 1/3 their previous weight is 1/3W. 98 pounds more than one-third his previous weight is 98 + 1/3W
So W - 28 = 98 + 1/3W
To solve, first add 28 to both sides of the equation
W - 28 = 98 + 1/3W
+28 +28
---------------------------
W = 126 + 1/3W
Now, subtract 1/3W from both sides:
W = 126 + 1/3W
-1/3W -1/3W
2/3W = 126
Now, multiply both sides by the reciprocal of 2/3 (which is 3/2)
2/3W = 126
x3/2 x3/2
W = 189 pounds
Let's double check:
If he loses 28 pounds, he would be 189 - 28 = 161
1/3 of his original 189 pounds is 63 pounds and 98 pounds more than that is 161 as well. We did it!