I'll try to explain, because I've had tubes before. In fact, I still have them.
For me, tubes were put in because of too many ear infections, and excessive water in my ear. The tube helped drain the water out. You can see A picture I have in a file. The tubes can be put I believe in the ear drum. They're put there to help drain water that has trouble getting out on its own.
The answer is “d” (1,000 kcal). As the trophic level increases energy is decreases by 10 times that of the previous level. If a system has 10,000 kcal, then the primary consumer have 10 times less (10,000/10) which is 1,000 kcal. The secondary consumers have 100 kcal and the tertiary have 10 kcal. Only 10% of the energy at each trophic level goes on to the next.
Explanation:
Option 1.
4y=12
Dividing 4 both sides
y=3
Division property should be used.
Option 2.

Cross multiplying each other,
y=12(4)
y=48
Option 3.
2(4y)=12
Opening bracktet in LHS
8y=12
Dividing both sides by 8 i.e.

Division property is used.
Option 4.
y+4=12
Subtracting both sides by 4 i.e.
Y+4-4=12-4
y=8
Subtraction property is used.
<em><u>It means that in option (4) Soo-Jung used the subtraction property of equality to solve an equation for y.</u></em>