Question 515003

B=-130P+640
the two points will be 
P,B
3, 250
4, 120
slope will be 250-120/3-4
130/-1
-130
b=mp+y
120=-130*4+y
120=-520+y
120+520=y
640=y
b=-130p+640
check
250=-130*3+640
250=-390+640
250=640-390
250=250
ok
120=-130*4+640
120=640-520
120=120
ok