What is the value of x 0.4x + 3.9 = 5.78

x = 4.7

Step-by-step explanation:

0.4x + 3.9 = 5.78

subtract 3.9 from each side

0.4x + 3.9-3.9 = 5.78-3.9

.4x = 1.88

divide by .4 on each side

.4x/.4 = 1.88/.4

x = 4.7

0.4x + 3.9 = 5.78       Subtract 3.9 on both sides

0.4x + 3.9 - 3.9 = 5.78 - 3.9

0.4x = 1.88      Divide 0.4 on both sides

x = 4.7

[proof]

0.4x + 3.9 = 5.78        Plug in 4.7 for "x"

0.4(4.7) + 3.9 = 5.78    

1.88 + 3.9 = 5.78

5.78 = 5.78

question: how many people can she serve?

answer: she can serve 16.66666667 people. so she can only give 16 people a complete serving.

question: does she have enough ice cream for her guests?

answer: no. explanation: she only has enough for 16 people to have a full serving. however, she can give a 17th person a partial serving.