Answer:
r=−5.3
Step-by-step explanation:
Step 1: Simplify both sides of the equation.
−7.4r−6.31=3.23−5.6r
−7.4r+−6.31=3.23+−5.6r
−7.4r−6.31=−5.6r+3.23
Step 2: Add 5.6r to both sides.
−7.4r−6.31+5.6r=−5.6r+3.23+5.6r
−1.8r−6.31=3.23
Step 3: Add 6.31 to both sides.
−1.8r−6.31+6.31=3.23+6.31
−1.8r=9.54
Step 4: Divide both sides by -1.8.
−1.8r/−1.8=9.54/−1.8
r=−5.3
Answer:
10,200
Step-by-step explanation:
Let's call the 13¢ stamps a and the 18¢ stamps b:
a+b = 42 and therefore a= 42-b (formula 1)
0.13a+0.18b= 6.66 In this formula, substitute the value of a according to formula 1:
0.13(42-b)+0.18b= 6.66 Multiply on the left to get rid of the parenthesis:
5.46-0.13b+0.18b= 6.66 Subtract 5.46 from both sides:
-0.13b+0.18b= 1.20 Add on the left:
0.05b= 1.20 Divide both sides by 0.05
b= 24 You have 24 18¢ stamps and:
42-24= 18 13¢ stamps
Check: (24 x 0.18) + (18 x 0.13)= 6.66 Correct.
