Final answer:
To find the value of r in the system of equations −8r − 8s = 100 and r − 2s = 10, we first solve the second equation for r in terms of s. We then substitute this value of r into the first equation and solve for s. The value of r is equal to -15/2.
Step-by-step explanation:
To find the value of r in the system of equations −8r − 8s = 100 and r − 2s = 10, we can use the second equation to solve for r in terms of s. Rearranging the equation gives: r = 2s + 10. Now, we can substitute this value of r into the first equation: −8(2s + 10) − 8s = 100. Simplifying this equation, we get: −16s − 80 − 8s = 100. Combining like terms, we have: −24s − 80 = 100. Adding 80 to both sides of the equation, we get: −24s = 180. Finally, dividing both sides by −24, we find that s = -15/2. Therefore, the value of r is also -15/2.