I need some help figuring out an affine cipher.

The only information I have is that

F is the ciphertext of E

C is the ciphertext of T

I know that encryption formula for the cipher is y = (ax + b ) MOD 26, where y is the ciphertext and x is the plaintext, and that decryption is

x = inverse(a)(y - b) MOD 26. If I insert the values for F->E and C->T then I get

F -> E	4 = inverse(a)(5 - b) MOD 26
C -> T	19 = inverse(a)(2 -b) MOD 26

How do I solve for a and b?