Y = 12% = 0.12
y = 100(0.05) + x(0.2) / 100 + x
0.12 = 5 + 0.2x / 100 + x
0.12( 100 + x ) = 5 + 0.2x
12 + 0.12x = 5 + 0.2x
7 = 0.08x
x = 87.5
hope this help
Formula for slope: 
y₂: 6
y₁: 8
x₂: 1
x₁: -2
Plug them into the slope equation:

--> 
---> 
The slope is
.
The sum is of n and 14 can be written as:
n+14=72