Solve the system of equations using substitution. 4x – y = 73y – 12x = –21

Rewrite the equations as 4x − y = 7 and 3y − 12x = −21. From the first equation, y = 4x − 7. Substituting into the second gives 3(4x − 7) − 12x = −21, which simplifies to −21 = −21. Since this is true for every value of x, the equations describe the same line and have infinitely many solutions: choice D, “infinite solutions.”

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