7th Grade Math

218 Equations and Inequalities

Examples 1, 2, and 4 Solve each equation. Check your solution.

1. 6 c = 18 2. 15 = 3 z 3. - 8 x = 24


2. 
   
   
   
   • 9 r = - 36 5.
   
   
   
   

p

_

9

= 9 6. _a

12

= - 3

Example 3 7. WORK Antonia earns $6 per hour helping her grandmother. Write and solve

an equation to find how many hours she needs to work to earn $48.

Example 5 8. SHARKS A shark can swim at an average speed of 25 miles per hour. At

this rate, how far can a shark swim in 2.4 hours? Use r = _dt.

= Step-by-Step Solutions begin on page R1.

Extra Practice begins on page EP2.

Examples 1, 2, and 4 Solve each equation. Check your solution.

9. 7 a = 49 10. 9 e = 27 11. 2 x = - 6


10. 
    
    
    
    • 4 j = 36 13. - 12 y = 60 14. - 4 s = - 16
      1515 _ 10 m^ =^7 16.^ u 6 =^9 17.^ -h 3 =^12
    
    
    
    


11. 
    
    
    
    • 30 =
    
    
    
    

q

_

• 5
  19. - 8 = _c
  
  
  • 10
    20. _r
    20
    = - 2
  
  
  
  

BAR DIAGRAM Write an equation. Use a bar diagram if needed. Then

solve the equation.

Example 3 21. MONEY Brandy wants to buy a digital camera that costs $300. If she saves

$15 each week, in how many weeks will she have enough money for the

camera?

22. COMPUTERS The width of a computer 15 in.

x

monitor is 1.25 times its height. Find

the height of the computer monitor

at the right.

Example 5 2323 SPEED A race car can travel at a rate of

205 miles per hour. At this rate, how far

would it travel in 3 hours? Use r = _dt.

24. INSECTS A dragonfly, the fastest insect,
    can fly a distance of 50 feet at a speed
    of 25 feet per second. Find the time in
    seconds. Use d = rt.

B 25. HURRICANES A certain hurricane travels at 20.88 kilometers per hour.

The distance from Cuba to Key West is 145 kilometers. Write and solve

a multiplication equation to find how long it would take the hurricane

to travel from Cuba to Key West.

214_226_C04L2_895130.indd 218 12/31/09 3:57 PM