The sequence is arithmetic as it goes down 3 every time
Arithmetic nth term formula is an=a1+d(n-1)
an=7-3(n-1)
an=7-3n+3
an=-3n+10
To find the 100th term substitute n for 100
a100=-3(100)+10
a100=-300+10
a100=-290
The 100th term is -290
So, hmmm keeping in mind that, an absolute value expression is in effect a piece-wise function, let's find its "slopes", the negarive slope on the left-side and the positive slope on the right side, and let's use the vertex point as our first point
what is the slope of a line that passes through (2, -1) and (0,7)

now, what is the slope of a line that passes through (2, -1) and (4,7)

since an absolute value expression is just a piece-wise with a +/- versions, then we can just combine those two.
The fraction would be 16/20
A ton is 2000 pounds. so it would be between 7 and 8 tons