Answer:
18 hours = £270
Explanation:
Find how much he charges per hour. Divide:
![(180)/(12)=15](https://img.qammunity.org/2021/formulas/mathematics/middle-school/lroa0k1th2rvfdvvoogxv47pzwmig7tsxr.png)
So ha charges about 15 an hour. Multiply this price by the number of hours:
![15*18=270](https://img.qammunity.org/2021/formulas/mathematics/middle-school/qd5io342pgxik5wxof4l9rlzimdgweku6g.png)
Therefore, he will charge £270 for a job that takes 18 hours.
OR
Set a proportional relationship since he charges a fixed amount:
![(price)/(time)=(price)/(time)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/ulxl1ltjzr2nwcxbynh09rw7ecx9lutbb0.png)
Insert the appropriate corresponding values:
![(180)/(12) =(x)/(18)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/a97mrxep0qsw18qsqsk58ljbx3og32oreu.png)
Solve for the price after 18 hours of work, represented by x. Cross multiply:
![12(x)=180(18)\\\\12x=3240](https://img.qammunity.org/2021/formulas/mathematics/middle-school/kg69w5w6ah04yb3xffr4nyp639pwet680w.png)
Solve for x. Use inverse operations to isolate the variable. Divide both sides by 12:
![(12x)/(12) =(3240)/(12) \\\\x=270](https://img.qammunity.org/2021/formulas/mathematics/middle-school/mqxxc7ovg5j3paobxndyqbloxiaxo9f2pi.png)
Therefore, after 18 hours, he will charge £270.
:Done