let

x = the number of 10 centavo coins, x>= 0

y = the number of 25 centavo coins, y>= 0

isaac has 80 pesos in 25 and 10 centavo coins:

x + y <= 80

he has 135 more 10 centavo coins than 25 centavo coins:

x = y + 135

by solving the system of equations:

x + y = 80

x = y + 135

x = 107.5

y = - 27.5

click here to see the step by step solution:

the solutions that we found are not integers.