Answer
Infinite solutions (all points along the line $d = 3a - 1$)
Work Step by Step
Given:
$9a - 3d = 3$
$-3a + d = -1$
Multiply the second equation by $3$: $-9a + 3d = -3$
Add equations: $9a - 3d + (-9a + 3d) = 3 + (-3)$
Expand: $9a - 9a - 3d + 3d = 3 - 3$
Simplify: $0 = 0$
Therefore infinite solutions.
Solve to make $d$ the subject:
Second: $-3a + d = -1$
Add $3a$: $d = 3a - 1$
Therefore infinite solutions, all points along the line $d = 3a - 1$
