Answer:
7
Step-by-step explanation:
set up your two equations.
j + a = 20. equation 1
j = a + 6. equation 2
since you know that j = a + 6, you can substitute a + 6 into the place of j. this is because you want to isolate a in order to find out how many problems andy completed.
j + a = 20
a + 6 + a = 20
now solve.
2a + 6 = 20
2a = 14
a = 7
andy has completed 7 problems. if juana completed 6 more than andy, then she has completed 13. 13 + 7 = 20.
