...Help?

x - 6y= 64 ... x = 6y + 64 ... sub into the second equation for x

7y - 4x= -84 ... 7y - 4(6y + 64) = -84 ... solve for y

0.1x + 0.5y= -2.4 ... multiply every term in both equations by 10 to clear the decimals, isolate x in the 1st equation, sub the result into the 2nd equation. same drill.

0.4x - 0.2y= 3.6