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x + y = 32 (1) (hours, counting Blake's working hours)
6.10*x + 7.20*y = 211.70 (2) (dollars, counting his earnings)
Multiply eq(1) by 6.10 (both sides). The modified (and equivalent) system is THIS:
6.10x + 6.10*y = 6.10*32 (3)
6.10*x + 7.20*y = 211.70 (4)
Now subtract eq(3) from eq(4) (both sides). The terms "6.10*x" will cancel each other,
and you will get a single equation for only ONE unknown y (it is how the Elimination method works)
7.20*y - 6.10*y = 211.70 - 6.10*32,
1.10y = 16.5 ====> y = = 15.
Answer. Blake worked 15 hours for B and 32-15 = 17 hours for A.
Solved.
On the way, you learned on how the Elimination method works.