9.87 x 10^7 - 2.5 x 10^6

answer in scientific notation

The right system is a + b ≥ 30 , b ≥ a + 10

Step-by-step explanation:

∵ The sum of them is at least 30 means the smallest value is 30

∴ Their sum is a + b = 30 or greater than 30

∴ a + b ≥ 30

∵ Their difference is at least 10 and the greater is b

∴ b - a = 10 or greater than 10

∴ b - a ≥ 10

∴ b ≥ a + 10

So the right system is the first answer

a + b ≥ 30 , b ≥ a + 10