Solve algebraically: 6a+3b=24, 3a-b=7

Equation 1 : 6a+3b=24Equation 2: 3a-b=7
Rearrange equation 2 to make b the subject:add b to both sides : 3a=7+bminus 7 from both sides: 3a-7=b
Substitute this into Equation 1 : 6a + 3(3a-7)=24
Multiply out the bracket: 6a + 9a - 21 = 24
Simplify:add the a terms together: 15a - 21=24add 21 to both sides: 15a=45divide by 15: a=3
Sub into Equation 2:3(3)-b=7multiply out bracket: 9-b=7add b to both sides: 9=7+bminus 7 from both sides: 2=b
Answer: a=3 b=2