Let's assume that the number of diners at the Italian restaurant is "x" and the number of diners at the Mexican restaurant is "y". Then, we can write the following equations based on the given information:
Italian restaurant:
Donation = $462 + $1 per diner
Donation = $462 + $1x
Mexican restaurant:
Donation = $235 + $2 per diner
Donation = $235 + $2y
Since both restaurants will donate the same total amount, we can set their donations equal to each other:
$462 + $1x = $235 + $2y
Simplifying this equation, we get:
$2y - $1x = $227
We know that the number of diners has to be a whole number, so we can try different values of x and see which one gives us a whole number for y.
For example, if we try x = 200, then we can solve for y:
$2y - $1(200) = $227
$2y = $427
y = 213.5
Since y is not a whole number, we need to try a different value of x. If we try x = 250, then we get:
$2y - $1(250) = $227
$2y = $477
y = 238.5
Again, y is not a whole number, so we try another value of x. If we try x = 300, then we get:
$2y - $1(300) = $227
$2y = $527
y = 263.5
Still not a whole number, so we try x = 350:
$2y - $1(350) = $227
$2y = $577
y = 288.5
Finally, we get a whole number for y, so we have our solution:
Italian restaurant: x = 350 diners, donation = $812
Mexican restaurant: y = 289 diners, donation = $812
Therefore, 350 diners promised to participate and each restaurant would donate $812.