Question 270225
Set-up:
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Mark drove for five hors total.
I wrote my equation in terms of his speed during the first three hours.
Equation:{{{3*X + 2*(X+10) = 245}}}

Solution:
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{{{3*X + 2*(X+10) = 245}}}Simplify
{{{3X + 2X + 20 = 245}}}Combine like terms
{{{5X + 20 = 245}}}Subtract 20 from both sides
{{{5X = 225}}} Divide both sides by 5
{{{highlight(X = 45)}}}
So now we know that Mark was going 45mph during the fist three hours of the trip.
Then the problem states that during the remaining two hours he went 10mph faster. So during the last two hours of the trip Mark was going 55mph.

Check the answer:
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Plug the values back into the equation
{{{3*X + 2*(X+10) = 245}}}
{{{3*(45) + 2*(55) = 245}}}
{{{135 + 110 = 225}}}
{{{highlight(225 = 225)}}}