Answer:
Roy is 10 years old at present and Joan is 5 years old at present
Step-by-step explanation:
Let
x----> Roy's age
y----> Joan's age
we know that
x=2y ----> equation A
(x+3)+(y+3)=21 ----> equation B
substitute equation A in equation B
(2y+3)+(y+3)=21
solve for y
3y+6=21
3y=21-6
3y=15
y=5 years
Find the value of x
x=2y ----> x=2(5)=10 years
therefore
Roy is 10 years old at present
Joan is 5 years old at present
Row A: x = 3
y = 2x - 3
y = 2(3) - 3 = 3 This is correct
Row B: x = 5
y = 2x - 3
y = 2(5) - 3 = 7 This is correct
Row C: x = 7
y = 2x - 3
y = 2(7) - 3 = 11 this is correct
Row D: x = 10
y = 2x - 3
y = 2(10) - 3 = 17 THIS IS INCORRECT, SO ROW D
