1. To solve this problem, you must make a System of equations.
 2. The equations are:
 d+g=22 (i)Â
 0.75d+1.25g=21 (ii)
 3. If you clear "d" from the equation (i), you have:
 d+g=22
 d=22-g
 4. Now, you must substitute d=22-g into the equation (ii):
 0.75d+1.25g=21
 0.75(22-g)+1.25g=21
 5. When you clear "g", you obtain its value:
 16.5-0.75+1.25g=21
 16.5+0.5g=21
 0.5g=21-16.5
 g=4.5/0.5
 g=9 Golden Delicious apples
 6. If you also want to know the value of "d", you can substitute g=9 into the equation (i) and clear "d":
 d+g=22
 d+9=22
 d=22-9
 d=13 Delicious apples
 How many Golden Delicious apples did Mary buy?
 The answer is: Mary bought 9 Golden Delicious apples.
