Let us represent the cost of day lilies by d and the cost of shrubs by s. We set up two equations,
Lea:
7d+6s=86
Kim:
9d+12s=132
Rearranging Lea's equation to make d the subject,
d= 86-6s /7
Substituting this value of d into Kim's equation:
9(86-6s /7) +12s=132
102s+12s=132
114s=132
s=1.16
Substituting this value into the original equation:
9d+12(1.16)=132
9d+13.92=132
9d=118
d=13.12
The cost of a day lily is $13.12 and the cost of a shrub is $1.16.
