22) Let w = how many weeks she needs to save. She makes 15 a week.
125 + 15w = 245
Subtract by 125 from both sides to get variables on one side of the equal sign and constants on the other.
15w = 245 - 125
15w = 120
Divide by 15 on both sides to isolate the variable w.
w = 120/15
w = 8
It will take her 8 weeks to buy the bike.
23) Let M = radius of mars. Earth's is 2981.1 km bigger.
m + 2981.1 = 6378.1
Subtract 2981.1 from both sides to get variables on one side and constants on the other.
m = 6378.1 - 2981.1
m = 3397.0
The radius of Mars is 3,397 km.
24) Let m = Maggie's age. Her brother is 3 years younger than twice her age; so 2m minus 3 years = 2m - 3
"sum... is 24" tells you to add the two together and have them equal 24.
m + 2m - 3 = 24
Combine like terms:
3m - 3 = 24
Add 3 from both sides to get variables on one side and constants on the other.
3m = 24 + 3
3m = 27
Divide by 3 to isolate the variable m
m = 27 / 3
m = 9
Maggie is 9 years old.