If I scored x, then Jeff scored 2x, and Mary scored 4x. x+2x+4x=7. Solve it.
7x=7 ---> x=1
I scored 1 run, Jeff scored 2 runs, and Mary scored 4 runs.
Hope the solution helped. Sometimes you need more than a solution. Contact fcabanski@hotmail.com for online, private tutoring, or personalized problem solving (quick for groups of problems.)