You can roll two dice at a time, a white one and a red one, and there are 36 different ways for the "up faces" to land. How many of ways will give a sum of 7 on the two up faces?
ways
r1,w6
r2,w5
r3,w4
r4,w3
r5,w2
r6,w1
r1,w6
r2,w5
r3,w4
r4,w3
r5,w2
r6,w1