7. Jairaj has 20 50-cent and 10-cent coins altogether. He has a total of $6.80 How many 50-cent coins does he have?

He will have 8 50-cent coins

Step-by-step explanation:

Let x = the number of 10-cent coins

Let y = the number of 50-cent coins

x + y = 20         y = 20 - x

[Set up an equation] .10x + .50y = 6.80

[Multiply both sides by 100] 10x + 50y = 680

[Plug-in] 10x + 50(20 - x) = 680

[Multiply] 10x + 1,000 - 50x = 680

[Combine like terms & subtract 1,000 from both sides] -40x = -320

[Divide both sides by -40] x = 8 coins

Have a nice day! - hopefully this is correct, I got a bit turned around for a bit lol

     I hope this is what you are looking for, but if not - comment! I will edit and update my answer accordingly. (ノ^∇^)

- Heather

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step-by-step explanation: