1. D
2. D
I don't know the answer to number 3 sorry.
You can model this with the equation 4x+3=15 since it is a number (x) times 4 with 3 added and equals 15.
Subtract 3 from both sides
4x=12
Divide both sides by 4
x=3
The is the concept of algebra, the weight of the spring can be modeled by the equation;
w=0.9sqrt E
where;
=energy in joules;
thus the weight of the spring when the energy is 12 j will be:
w=0.9sqrt12
w=3.18 g
What? I don’t understand what you’re asking.