A pound of oranges costs $2 less than a pound of pears. Together, ten pounds of oranges and eight pounds of pears cost $61. How much would three pounds of pears cost?

Let us say that:

o = cost of oranges per pound

p = cost of pears per pound

so that:

o = p - 2

Therefore:

10o + 8p = 61

10 (p - 2) + 8p = 61

10p - 20 + 8p = 61

18p = 81

p = 4.5

p = $4.5 per pound

So 3 pounds of pears would cost:

total cost = 3 * 4.5

total cost = $13.5