Turn it into a "two-equation, two-unknown" setup, and knock it out that way.

Withplaying the role of the market expected return, andmstarring as the risk-free rate, Wal-Mart's expected return sets up as...r

0.12 =r+ 1.1(m-r)

...and Dell's equation is

0.123 =r+ 1.2(m-r)

Solve that system forand form, and you'll see it agrees with the given answers. Cheers!r