{
  "problem": "$ { {-4} \\times \\left[\\begin{array}{r}{1} \\\\ {3} \\\\ {1}\\end{array}\\right] = {?} } $",
  "hints": [
    "To multiply a matrix by a number, multiply each item of the matrix by the number.",
    "${\\left[\\begin{array}{r}{-4}\\times{1} \\\\ {-4}\\times{3} \\\\ {-4}\\times{1}\\end{array}\\right]}$",
    "Now, simplify: ${\\left[\\begin{array}{r}{-4} \\\\ {-12} \\\\ {-4}\\end{array}\\right]}$"
  ]
}
{'source': 'AMPS', 'file': 'amps/khan/476/1608190399.json'}