Lena bought a total of 20 postcards. She bought 6 more large postcards than small. Write a system of equations that represents the postcards Lena purchased. Solve the system by substitution. Interpret the solution.

X = small postcards

y = large postcars

x+y=20

y=x+6

x + (x+6) = 20

x + x + 6 = 20

2x = 20-6

2x=14 / : 2

x = 7. - - > the number of small postcards is 7.

x+y=20

7+y=20

y=20-7

y=13 - - > the number of large postcards is 13.

also y=x+6 = 7+6=13.