Question

se 3a + 8b = 45 & 5a + 6b = 53, Determine o valor de a - b.

Answer 1

vc coloca em sistema 
3a+8b=45  (x -5)
5a+6b=53  ( x 3)                             substituindo b em a-
---------------                                       -15a -40b= -225
-15a-40b= - 225                               -15a -40. 3= -225
15a+16b= 159                               -15a -120 = -225
 --------------------                                -15a = -225 + 120
- 22b = -66                                      -15a = -105b= 66/22                                          a= 105/15
b=3                                                  a= 7
Espero ter Ajudado!!!