multiply both sides of the first equation by 3 and multiply both sides of the second equation by 2 to get:
6T + 9C = 10500
6T + 4C = 8000
subtract the second equation from the first to get:
5C = 2500
solve for C to get C = 500.
use either one of the original equations and replace C with 500 and solve for T.
first original equation is 2T + 3C = 3500
replace C with 500 to get 2T + 1500 = 3500
subtract 1500 from both sides of this equation to get 2T = 2000
solve for T to get T = 1000
you have T = 1000 and C = 500.
go back to the original equations and evaluate to determine if the solution is correct.
2T + 3C = 3500 becomes 2*1000 + 3*500 = 3500 which becomes 2000 + 1500 = 3500 which becomes 3500 = 3500 which confirms the solution is correct for the first equation.
3T + 2C = 4000 becomes 3*1000 + 2*500 = 4000 which becomes 3000 + 1000 = 4000 which becomes 4000 = 4000 which confirms the solution is correct for the second equation.