Question

Dory and nemo go to Taco Bell for lunch.dory orders three soft tacos and three double deckers for $11.25 nemo pays $10.00 for four soft tacos and two double deckers .write a system of equations that represents the lunch orders for dory an
d memo use x to represented soft tacos an y to represent double deckers

Answer 1

S= soft taco
d= double deckers

$11.25= 3s+3d
$10.00= 4s+2d
first eliminate 1 variable, lets say d ,to do this we must cancel them out, to do this multiply the top by -2 and the bottom by 3
  -2 ($11.25= 3s+3d)                                      -$22.50= -6s-6d
  3 ($10.00= 4s+2d)     which becomes...          $30.00=12s+6d
then the -6d and the positive 6d cancel out and you are left with 1 variable 
after this add the remaining parts to get...
$7.50=6s  divide by 6, then put s back into one of your original equations and solve for d then you have found how much each item costs and are finished with the system of equations