Solve, using the substitution method. j + k = 3 j – k = 7

the solution is (8, 1).

the solution is (5, –2).

there is no solution.

there are an infinite number of solutions.

The solution is (5, -2)
Take the second equation and rewrite it as j = k + 7
Next plug this into the first equation in place of the j.
SO...k + 7 + k = 3
2k + 7 = 3
subtract 7 from both sides
2k + 7 -7 = 3 - 7
2k = -4
divide both sides by 2
k = -2
Plug -2 back in to the equation j = k + 7
j = -2 + 7
j = 5

Is there more to the question?