Answer:
(a, b) = (-8, -29)
Step-by-step explanation:
The two relations can be written as the equations ...
a - b = 21
5a -2b = 18
Subtracting 2 times the first equation from the second, we have ...
(5a -2b) -2(a -b) = (18) -2(21)
3a = -24 . . . . . simplify
a = -8 . . . . . . . divide by 3
Substituting into the first equation, we have ...
-8 -b = 21
-b = 29 . . . . . . add 8
b = -29 . . . . . . multiply by -1
The values of a and b are -8 and -29, respectively.
