Answer:
- engineering vs business: 3 years
- engineering vs biology: 8 years
Explanation:
Write expressions for the number of students in each major. Then write the equation needed to relate them the way the problem statement says they are related.
For year y, the number of students in each major is ...
- engineering: 120 +22y
- business: 105 -4y
- biology: 98 +6y
1) Engineering is twice Business:
120 +22y = 2(105 -4y) . . . . . Engineering is double Business in year y
120 +22y = 210 -8y . . . . . . . eliminate parentheses
120 +30y = 210 . . . . . . . . . . add 8y
4 + y = 7 . . . . . . . . . . . . . . . . divide by 30
y = 3 . . . . . . . . subtract 4
In 3 years there will be 2 times as many students majoring in Engineering than in Business.
__
2) Engineering is twice Biology:
120 +22y = 2(98 +6y) . . . . Engineering is double Biology in year y
120 +22y = 196 +12y . . . . . eliminate parentheses
120 +10y = 196 . . . . . . . . . . subtract 12y
10y = 76 . . . . . . . . . . . . . . . .subtract 120
y = 7.6 . . . . . . divide by 10
In 8 years there will be 2 times as many students majoring in Engineering than in Biology.