1. To solve this problem, you must make a System of equations.
2. The equations are:
d+g=22 (i)
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.